Reduced neutrophil superoxide production among healthy older adults in response to acute psychological stress

Ageing is associated with higher morbidity and mortality, and declining immune function, termed immunesenescence. The present study examined the effects of an acute laboratory psychological stress task on innate immunity, specifically neutrophil function, among older adults. The two functional assays used were phagocytosis of Escherichia coli and stimulated superoxide production. Participants were 17 (11 female) older adults (mean age 75.7, SD = 7.06 years). Blood samples to determine neutrophil function by flow cytometry were taken at the end of resting baseline, during an acute stress task and during recovery. The stress task was an 8-minute time-pressured mental arithmetic challenge with social evaluation. There was a significant reduction in neutrophil superoxide production, p = .017, η²_p = .240, associated with the stress task relative to baseline, but no effect on phagocytosis. The results of this study could contribute to explaining the increased risk of infection in older adults, particularly those subject to frequent stress exposures. Future research is needed to explore the underlying mechanisms of acute stress effects on human neutrophil function in older adults in greater detail.     

Aerobic exercise training and cardiovascular reactivity to psychological stress in sedentary young normotensive men and women

Forty-five (22 women) sedentary young (18-30 years old) nonsmoking normotensive volunteers engaged in either 6 weeks of aerobic training (AT), weight training (WT), or a no-treatment (NT) condition to determine whether AT lowers systolic (SBP) and diastolic (DBP) blood pressure, heart rate (HR), and rate-pressure product (RPP) during rest, psychological stress, and recovery periods. Estimated VO(2)max increased for the AT (32.1+/-1.1 to 38.4+/-1.0 ml.kg(-1).min(-1)). A smaller increase for the WT (30.5+/-1.1 to 33.8+/-1.0) was likely due to increased leg strength, and VO(2)max did not change for the NT (32.5+/-1.1 to 32.9+/-1.0). Heart rate and RPP levels were lower during psychological stress and recovery after training for AT relative to the WT and NT. Overall SBP was also lower in the AT relative to the NT but not the WT. In conclusion, aerobic training lowered cardiovascular activity levels during psychological stress and recovery in healthy young adults, implying a protective role against age-related increases in coronary heart disease for individuals who adopt aerobic exercise early in life and maintain the behavior across the life span.     

Temporal stability of lipid responses to acute psychological stress in middle-aged men

The purpose of this study was to establish the temporal stability of lipid responses to acute psychological stress. Eighteen men were tested twice an average of 16.2 months apart in identical laboratory reactivity protocols. Total cholesterol, triglycerides, high- and low-density lipoprotein-cholesterol, plasma volume, heart rate, and blood pressure were assessed during rest, serial subtraction, and speech. After correction for changes in plasma volume, significant elevations were recorded for all variables during the speech task, but fewer variables showed changes during the serial subtraction task. Strong intersession associations were found when considering levels of the variables during baseline and stress (rs≥58). Correlations for the change scores ranged from .36 to .52 for the atherogenic lipids and from .39 to .87 for the cardiovascular variables. Little evidence was found for stability of plasma volume changes. There is moderate to high temporal stability of the atherogenic lipids when considering rest and stress levels and small to moderate temporal stability when considering change scores.     

Hypertension risk factors and cardiovascular reactivity to mental stress in young men

Hypertension risk may be associated with increased pressor response to mental stress. However, studies using family history as a predictor of reactivity have obtained mixed results. We assessed cardiovascular responses to mental arithmetic stress (a 5-min serial subtraction task) in male medical students (n = 220) at three levels of hypertension risk based on parental history and the subject's systolic blood pressure (SBP): low (SBP < 125 mm Hg and 0 or 1 hypertensive parent), moderate (resting SBP ≥ 125 mm Hg or 2 hypertensive parents), or high (resting SBP ≥ 125 mm Hg and 1 or 2 hypertensive parents). High risk men showed the greatest blood pressure responses ( + 22/ + 16 mm Hg), while moderate and low-risk groups showed correspondingly smaller responses ( + 17/ + 13 and + 14/ + 11 mm Hg, p's < 0.02). Family history alone did not predict differential reactivity. This study replicates and extends our previous work suggesting the importance of using both family history and resting blood pressure level in determining future risk for hypertension in studies of cardiovascular reactivity in relation to hypertension risk in males.     

Sex differences in the interleukin-6 response to acute psychological stress

Interleukin-6 (IL-6), an immune regulator that helps coordinate the inflammatory response, may mediate inflammatory disease exacerbation associated with stress. Twenty men and twenty women completed a single session, comprising baseline (20 min), mental arithmetic task (8 min), and recovery (60 min). Blood samples, taken at baseline, immediately after the task, and at +30 and +60 min recovery were analysed for plasma IL-6. Overall, IL-6 increased linearly from baseline to +60 min recovery, and a sex difference was found in the IL-6 response, with men peaking earlier than women. These findings confirm a small delayed IL-6 increase after acute laboratory stress, and reveal sex differences in the profile of the IL-6 response.     

Differences in neutrophil function in young and mature cattle and their response to IFN-γ

Neutrophils from young calves (2-4 months old) had significantly lower iodination, oxidative metabolism, chemotaxis and random migration, but higher antibody-independent cell-mediated cytotoxicity (AINC) activity than neutrophils from mature cattle (2–3-years old). Antibody-dependent cell-mediated cytotoxicity (ADCC) and oxidative metabolism were enhanced, and random migration was diminished in both groups by in vitro recombinant bovine IFN-γ (rboIFN-γ) treatment. Neutrophils from both groups had enhanced AINC activity and reduced chemotactic responsiveness after incubation in rboIFN-γ, however, these differences were significant only in the mature cattle. RboIFN-γ decreased the cytoplasmic Ca²⁺ flux in both groups. Neutrophils from young calves had lower cytochrome c reduction and iodination activity than mature cattle in response to both phorbol myristate acetate and opsonised zymosan. Lysed neutrophils from young calves had significantly less myeloperoxidase activity than those from mature cattle. It was also observed that the size of neutrophils increased with age in calves.     

Augmented sympathetic nerve activity in response to stressors in young borderline hypertensive men

To determine whether there may be an abnormality in sympathetic nerve activity in response to physical and psychological stressors, we microneurologically recorded muscle sympathetic nerve activity in 11 normotensive and 9 borderline hypertensive, age-matched men. Supine blood pressure, plasma levels of epinephrine and norepinephrine and muscle sympathetic nerve activity were measured before and during a cold pressor test or a mental arithmetic test. The resting basal values of muscle sympathetic nerve activity, blood pressure and plasma epinephrine were significantly higher in the borderline hypertensives than in the normotensives (P less than 0.05). Plasma norepinephrine levels tended to be higher in the borderline hypertensives than in the normotensives but not to a significant extent (P less than 0.10). The cold test produced significantly exaggerated pressor and muscle sympathetic nerve responses (P less than 0.05) with a trend towards an increase in plasma norepinephrine (P less than 0.10) in the borderline hypertensives as compared with normotensives. The mental arithmetic test produced significantly enhanced pressor and plasma epinephrine responses in the borderline hypertensives as compared with the normotensives (P less than 0.05). During the mental arithmetic test the muscle sympathetic nerve activity decreased significantly in the normotensives (P less than 0.05) but not in the borderline hypertensives. These findings indicate that in people with borderline hypertension an abnormality exists in sympathetic nerve activity at rest and in response to stressors.     

Effects of manipulating the amount of social-evaluative threat on the cortisol stress response in young healthy men

Perceived social-evaluative threat triggers the hypothalamic-pituitary adrenal (HPA) axis, resulting in cortisol release. The current study examined the effects of varying the levels of social-evaluative threat on the stress response. Sixty healthy men (mean age + 23.17 +/- 3.89 years) underwent a public speaking task. Four conditions were established on the basis of panel location (inside or outside the room) and number of panelists (one or two). It was hypothesized that these variations affect salivary cortisol and physiological responses in a gradient manner. The task elicited significant cortisol and blood pressure changes for all conditions, but no difference between the groups was found, suggesting that all conditions were equally stressful. Study conclusions were that, for men, the visual presence of a panel is not necessary to elicit a cortisol response. Furthermore, increasing the number of judges does not increase the intensity of the stress response in a gradual manner, but rather seems to follow a threshold pattern. Future studies should include women and try to define the possible threshold to activate the HPA axis.     

A heartfelt response: Oxytocin effects on response to social stress in men and women

Background

Animal research indicates that oxytocin is involved in social behavior, stress regulation, and positive physiologic adaptation. This study examines whether oxytocin enhances adaptive responses to social stress and compares effects between men and women.

Methods

Hypotheses were tested with a placebo-controlled, double-blind experiment. Social stress was induced. Changes in cardiovascular reactivity, affect, and behavior were assessed.

Results

Participants given oxytocin, relative to placebo, responded to social stress with a challenge orientation characterized by a benign pattern of cardiovascular reactivity. Gender differences emerged. Men given oxytocin reported less negative affect and had greater vagal rebound, while women given oxytocin reported more anger and had better math performance following social stress.

Discussion

Findings indicate oxytocin stimulates an approach-oriented cardiovascular profile during social stress, suggesting mechanisms by which oxytocin might improve physical health. However, before considering oxytocin as therapeutic or uniformly enhancing health, greater understanding of possible gender differences in effects is needed.     

Cardiac response to exercise in young,normal weight and overweight men and women

Overweight and obesity are associated with hemodynamic changes at rest. Whether these changes are mirrored during exercise is uncertain. We compared cardiac output (Q) and stroke volume (SV) in 12 overweight (OW) and 12 normal weight (NW) adults at rest and during exercise. Participants were assessed for body composition, peak oxygen consumption, and Q and SV at rest and during cycling exercise at 50, 75 and 100 W. Cardiac output was significantly higher at rest and during exercise in OW than NW when fat mass and ethnicity were used as covariates. When fat free mass was added as a covariate, Q was no longer different between groups. Stroke volume tended to be higher in OW than NW when fat mass and ethnicity were used as covariates (P = 0.055) with no differences in heart rate observed. Although the total change in Q and SV was similar between groups with each exercise intensity, overall Q was higher in the OW than NW participants. The higher Q is likely explained by a higher SV, secondary to a greater blood volume in the OW. The elevated hemodynamic response in OW may reflect the early cardiac adaptations of excess body mass. University of Texas Research Institute funded part of this study.     

DHEA and DHEA-S response to acute psychosocial stress in healthy men and women

This study investigates the effect of acute psychosocial stress on serum concentrations of DHEA and DHEA-S in healthy men and women. Twenty men and 19 women (age 30-50 years) underwent Trier Social Stress Test (TSST). Physiological measurements were performed before, directly after the stress test and after 30 mins of recovery. In both men and women, significantly elevated DHEA and DHEA-S levels were observed in response to the stressor. There was a large inter-individual variation in the magnitude of the response, especially for DHEA but no statistical difference between men and women. Magnitude of the change in the levels of DHEA was found to be positively associated with the magnitude of the changes in ACTH, cortisol and heart rate. Furthermore, the results of this study suggest that the capacity to secrete DHEA and DHEA-S during acute psychosocial stress declines with age.     

Physiological stress response of young adults exposed to bullying during adolescence

Peer victimization in the form of bullying is a chronic social stressor experienced by many humans during development. Exposure to bullying has been associated with a variety of mental disorders, such as anxiety and depression. Participants pre-selected for the presence or absence of a history of being bullied were brought into a laboratory and placed in a stressful situation. Blood pressure, heart rate, and salivary cortisol levels were measured before the introduction of the stressor (Time 1), at the end of the stressor (Time 2), and after its removal (Time 3). Men with a history of exposure to frequent bullying showed blunted blood pressure responses at Time 2 compared to control men. Bullied and Non-bullied women did not show any differences in any of the measures. Men and women in both groups showed an increase in heart rate in response to the stressor. There were no significant differences in salivary cortisol levels between Bullied and Non-bullied participants. However, salivary cortisol levels and systolic blood pressure were lower in Bullied male participants who reported having no feelings of anger about their experience compared to controls and those who did report anger. These data show altered sympathetic responses to stress in men with a history of victimization as well as suggesting long-term effects on the HPA axis in the most affected individuals.     

Effects of panel sex composition on the physiological stress responses to psychosocial stress in healthy young men and women

Men and women differ in regard to psychosocial stress responses. Biological and contextual factors are known to mediate these differences; however, few studies investigated their interaction. In the present study, we examined contributions of both contextual and biological factors to the stress response of young healthy adults. Men and women were exposed to a modified version of Trier Social Stress Test. The participants gave a speech in front of a panel of judges, composed of either male or female panelists. Both men, and women presented a cortisol increase only when exposed to opposite sex panelists. Interestingly, this effect was only observed in women in their follicular phase. This finding showed that the induction of a psychosocial stress response does not strictly rely on direct social evaluation, but also depends on the sex composition of the panel. Implications for future studies are discussed.