Gender differences in stimulated cytokine production following acute psychological stress

Inflammatory and Cardiovascular Responses to Active and Passive Acute Psychological Stress

OBJECTIVE

Acute psychological stress is a risk factor for cardiovascular disease (CVD), possibly through promoting a heightened inflammatory profile. Active stressors are commonly used to investigate cardiovascular and immune reactivity; however, this response may not translate to other stress modalities. We aimed to decipher potential differences in immune responses to passive and active stressors.

METHODS

Eighty-eight participants completed this study. After a baseline period, a passive (International Affective Picture System [IAPS]) and active stress task (Paced Auditory Serial Addition Test [PASAT]) were completed in a randomized order, with 45-minute rest post-tasks. Cardiovascular measures (including SBP, DBP, HR) were collected continuously. Blood samples were collected after each time point determining inflammatory responses, including circulating and stimulated interleukin-6 (IL-6), systemic inflammation response index (SIRI), neutrophil/lymphocyte ratio (NLR), TNF-α, and P- and E-selectin.

RESULTS

Cardiovascular measures were higher during the PASAT than IAPS (p < .001). Circulating IL-6 levels increased from baseline to 45-minutes after both tasks (p ≤ .001), with no difference between 45-minute post-PASAT and 45-minute post-IAPS (p > .05). SIRI increased from baseline to post-IAPS (p = .013), 45-minute post-IAPS (p = .004), and 45-minute post-PASAT (p < .001). No difference in SIRI between 45-minute post-PASAT and 45-minute post-IAPS existed. NLR increased from baseline to 45-minute post-PASAT (p = .008). There were no significant time effects for TNF-α, P-selectin, or E-selectin (all p > .05).

CONCLUSION

Both stressors increased circulating IL-6 levels and SIRI. Cardiovascular measures were higher during the active task, but the magnitude of inflammatory responses did not significantly differ between tasks. Regardless of stress modality, an immune response ensues, potentially increasing the risk of CVD over time.

The Energetic Stress Marker GDF15 is Induced by Acute Psychosocial Stress

GDF15 (growth differentiation factor 15) is a marker of cellular and mitochondrial energetic stress linked to physical-mental illness, aging, and mortality. Here, we describe the psychobiological regulation of plasma and saliva GDF15 in four human studies including 3,599 samples from 148 healthy individuals. We report two main observations establishing GDF15 as a novel tractable biomarker of psychosocial stress. 1) In two experimental laboratory studies, socio-evaluative stress rapidly elevates GDF15 and lactate, two molecular markers of energetic/reductive stress. 2) Similar to other stress-related metabolic hormones, we also find that saliva GDF15 exhibit a robust awakening response, being highest at the time of waking up and declining by ~42-92% within 30-45 minutes. These data position GDF15 as a dynamic biomarker of psychosocial stress accessible in human blood and saliva, pointing towards a shared psychobiological pathway linking mental and mitochondrial energetic stress. These foundational observations open the door to large-scale studies using GDF15 to non-invasively probe how acute psychosocial factors promote cellular and mitochondrial and energetic stress contributing to the stress-disease cascade across the lifespan.

A Brief Historic Review of Research on Early Life Stress and Inflammation across the Lifespan

BACKGROUND

Extensive evidence from animal and human studies indicates that exposure to stress during sensitive developmental periods significantly increases the risk for psychiatric and physical disorders, resulting in reduced longevity. Chronic immune activation has been suggested as one pathway through which early adverse experiences may become biologically embedded. This paper highlights selected key findings and questions that first emerged in the literature and founded the field and then examines how research methods and questions have evolved over time.

SUMMARY

During the past decades, evidence from preclinical, clinical, and epidemiological studies has accumulated suggesting consequences of early life stress (ELS) exposure for immune function, particularly increased chronic inflammation or inflammatory responses. Scientific approaches to study the effects of ELS on the immune system have changed since the first studies on this topic were published.

KEY MESSAGES

Across different study designs, species, and methods, a consistent association between childhood adversity and a pro-inflammatory phenotype has been reported. We critically discuss which topics warrant further consideration and how current findings could be used to develop targeted interventions to prevent or reverse the biological embedding of ELS and resultant disease manifestations.

Growth differentiation factor 15 and malnutrition in older adults

OBJECTIVES

Growth differentiation factor 15 (GDF-15) levels increase due to systemic inflammation and chronic disease burden. Since these biological processes are pathogenic factors of malnutrition, we examined the prospective association between GDF-15 serum levels and subsequent malnutrition in older adults.

METHODS

We used data from 723 women and 735 men aged ≥65 years [mean age (SD): 71.3 (4.18) years] participating in the Seniors-ENRICA-2 cohort, who were followed-up for 2.2 years. Malnutrition was assessed with the Mini Nutritional Assessment-Short form (MNA-SF), where a 12-14 score indicates normal nutritional status, an 8-11 score indicates at risk of malnutrition, and a 0-7 score malnutrition. Associations of GDF-15 and malnutrition were analyzed, separately in women and men, using linear and logistic regression and adjusted for the main potential confounders.

RESULTS

The mean (SD) MNA-SF score at baseline was 13.2 (1.34) for women and 13.5 (1.13) for men. Incident malnutrition (combined endpoint "at risk of malnutrition or malnutrition") over 2.2 years was identified in 55 (9.7%) of women and 38 (5.4%) of men. In women, GDF-15 was linearly associated with a decrease in the MNA-SF score; mean differences (95% confidence interval) in the MNA-SF score were -0.07 (-0.13; -0.01) points per 25% increase in GDF-15, and -0.49 (-0.83; -0.16) for the highest versus lowest quartile of GDF-15. Also in women, GDF-15 was linearly associated with a higher malnutrition incidence, with odds ratio (95% confidence interval) of 1.24 (1.06; 1.46) per 25% increment in GDF-15 and of 3.05 (1.21; 7.65) for the highest versus lowest quartile of GDF-15. Results were similar after excluding subjects with cardiovascular disease and diabetes. No association of GDF-15 with changes in MNA score or malnutrition incidence was found in men.

CONCLUSION

Higher serum GDF-15 concentrations are associated with worsening nutritional status in older women. Further studies should elucidate the reasons for the sex differences in this association and explore the therapeutic potential of modifying GDF-15 to prevent malnutrition.

The Psychoneuroimmunological Model of Moral Distress and Health in Healthcare Workers: Toward Individual and System-Level Solutions

Healthcare is presently experiencing a global workforce crisis, marked by the inability of hospitals to retain qualified healthcare workers. Indeed, poor working conditions and staff shortages have contributed to structural collapse and placed a heavy toll on healthcare workers' (HCWs) well-being, with many suffering from stress, exhaustion, demoralization, and burnout. An additional factor driving qualified HCWs away is the repeated experience of moral distress, or the inability to act according to internally held moral values and perceived ethical obligations due to internal and external constraints. Despite general awareness of this crisis, we currently lack an organized understanding of how stress leads to poor health, wellbeing, and performance in healthcare workers. To address this critical issue, we first review the literature on moral distress, stress, and health in HCWs. Second, we summarize the biobehavioral pathways linking occupational and interpersonal stressors to health in this population, focusing on neuroendocrine, immune, genetic, and epigenetic processes. Third, we propose a novel Psychoneuroimmunological Model of Moral Distress and Health in HCWs based on this literature. Finally, we discuss evidence-based individual- and system-level interventions for preventing stress and promoting resilience at work. Throughout this review, we underscore that stress levels in HCWs are a major public health concern, and that a combination of system-level and individual-level interventions are necessary to address preventable health care harm and foster resilience in this population, including new health policies, mental health initiatives, and additional translational research.

Brain-derived subgroups of bipolar II depression associate with inflammation and choroid plexus morphology

AIM

Elevated inflammation and larger choroid plexus (ChP) volume has been previously identified in mood disorders. Connections between inflammation, ChP, and clinical symptoms in bipolar II depression (BDII-D) are unclear. Data-driven clustering based on neuroanatomical phenotypes may help to elucidate neurobiological associations in BDII-D.

METHODS

Inflammatory cytokines, clinical symptoms, and neuroanatomical features were assessed in 150 BDII-D patients. Sixty-eight cortical surface area (SA) and 19 subcortical volumes were extracted using FreeSurfer. The ChP volume was segmented manually using 3D Slicer. Regularized canonical correlation analysis was used to identify significantly correlated components between cortical SA and subcortical volumes (excluding the ChP), followed by k-means clustering to define brain-derived subgroups of BDII-D. Low-grade inflammation was derived by averaging the standardized z scores of interleukin (IL)-6, IL-1β, and tumor necrosis factor-α (TNF-α), which were computed to create a composite z-value score. Partial Pearson correlations followed by multiple comparison correction were conducted to explore associations between inflammation, clinical symptoms, and ChP volume.

RESULTS

Subgroup I demonstrated smaller subcortical volume and cortical SA, higher inflammation, and larger ChP volume compared with subgroup II. Greater ChP volume was associated with a higher low-grade inflammation (mean r = 0.289, q = 0.003), CRP (mean r = 0.249, q = 0.007), IL-6 (left r = 0.200, q = 0.03), and TNF-α (right r = 0.226, q = 0.01), while greater IL-1β was significantly associated with severe depressive symptoms in BDII-D (r = 0.218, q = 0.045).

CONCLUSIONS

Neuroanatomically-derived subgroups of BDII-D differed in their inflammation levels and ChP volume. These findings suggest an important role of elevated peripheral inflammation and larger ChP in BDII-D.

Older adults' self-reported prospective memory lapses in everyday life: Connections to inflammation and gender

OBJECTIVE

Limited research has focused on the association between inflammatory markers and features of subjective cognitive functioning among older adults. The present work examined links between inflammation and a specific subjective cognitive report: prospective memory (PM), or our memory for future intentions, such as attending an appointment or taking medication.

METHOD

We assessed self-reported PM lapses using a two-week ecological momentary assessment (EMA) diary protocol via smartphone as well as levels of blood-based inflammation among 231 dementia-free older adults (70-90 years, 66% women) enrolled in the Einstein Aging Study.

RESULTS

Overall, PM lapses were largely unrelated to inflammatory markers. However, a significant gender difference was observed in the link between basal levels of interleukin (IL)-8 and PM lapses: higher levels of basal IL-8 were associated with more PM lapses among men (estimate = 0.98, 95%CI: [0.43, 1.53], p < .001) but not women (estimate = -0.03, 95%CI: [-0.45, 0.39], p = .826). No other significant relationships between PM lapses and basal or stimulated (ex vivo) cytokine levels (IL-1β, IL-4, IL-6, IL-8, IL-10, tumor necrosis factor-alpha [TNF-α]) or C-reactive protein (CRP) emerged.

CONCLUSION

Elevated levels of IL-8 in older men may possibly be an early indicator of neurodegeneration that relates to PM performance. Future studies should continue to examine PM and inflammation across genders to identify possible mechanisms through which these constructs may indicate neurodegeneration and dementia risk.

Distinct dynamic behavioural response to social exclusion in male patients with a history of alcohol dependence

Social exclusion contributes to alcohol consumption, whereas the development of alcohol dependence (AD) can in turn lead to the social exclusion of people with AD. Previous research observed altered neural responses to experimentally induced social exclusion (i.e., Cyberball game) in patients with AD. In addition, inflammation has been associated with both social behaviours and AD. Our study aimed to investigate the dynamic behavioural response and the inflammatory effects of social exclusion in male patients with a history of AD. To this end, we analysed dynamic changes in ball tossing during a partial exclusion Cyberball game and the cytokine interleukin (IL)-1b in saliva in 31 male patients who had a history of AD and 29 gender-matched healthy controls without AD. Participants were included in the first 2 min of the Cyberball game and then excluded by one of the two co-players in the proceeding 5 min. Saliva was collected three times: one before and two after the Cyberball game. Across groups, participants passed the ball more often to the excluder during the partial exclusion period. Analysis using piece-wise linear mixed models showed that patients rapidly increased ball tosses to the excluder upon exclusion, which lasted to the late response phase, whereas the early behavioural response to exclusion took longer for controls. There was no significant change of salivary IL-1b level to exclusion in either patients or controls. The results indicate a distinct dynamic behavioural response to social exclusion in male patients with a history of AD.

Short bouts of walking attenuates the response of IL-8 to prolonged sitting in healthy adults

PURPOSE

Experimental studies have shown that prolonged sitting for 2-8 h can cause changes to vascular and metabolic markers; the response of pro-inflammatory cytokines is relatively unexplored. The purpose of this study is to determine the response of interleukin-8 (IL-8) to prolonged and interrupted sitting.

METHODS

Healthy participants (n = 24, 21.1 years ± 2.2, 50% female) completed a prolonged sitting session (4 h) and an interrupted sitting session (4 h of sitting with 3 min of walking at 60%HRmax, every 30 min) in random order. Saliva and capillary plasma were collected at the beginning (T1) and at the end of each session (T2).

RESULTS

Salivary concentrations of IL-8 increased during the prolonged (T1 median: 22.09 pg/mL, T2 median: 86.18 pg/mL; p =  < 0.01, ES - 0.55) and interrupted (T1 median: 22.09 pg/mL, T2 median: 51.99 pg/mL; p = 0.021, ES - 0.34) sessions; however, the increase during interrupted sitting was lower (PS median: 134.4%, range: - 43.96 to 1115.69 and IS median: 50.8%, range: - 75.5 to 356.35; p = 0.011, ES - 0.53). In the sub-sample of males, salivary IL-8 did not increase in the interrupted session (T1 median: 22.09, range: 3.496-699.12, and T2 median: 24.96, range: 5.11-533.5, p =  > 0.05, ES - 0.16). No significant findings were observed for IL-8 in the plasma.

CONCLUSION

Prolonged sitting appears to increase concentrations of the pro-inflammatory cytokine IL-8 while interrupting this sitting with short bouts of walking blunts this response. Sex appears to moderate this relationship; however, there appears to be a large amount of individual variability.

Gut Bless Your Pain—Roles of the Gut Microbiota, Sleep, and Melatonin in Chronic Orofacial Pain and Depression

Background. Increased attention has been paid to the gut–brain axis recently, but little is known so far regarding how this translates into pain susceptibility. Aim. The aim of this review is to determine whether gastroenterological disorders and sleep disorders (directly or indirectly) contribute to an increased susceptibility to depression and chronic orofacial pain. Method. A search was performed in the U.S. National Library of Medicine (PubMed) database in order to find studies published before 19 December 2021. We used the following terms: gut microbiome, OR sleep quality, OR melatonin, OR GERD, OR IBS, AND: depression OR chronic pain, in different configurations. Only papers in English were selected. Given the large number of papers retrieved in the search, their findings were described and organized narratively. Results. A link exists between sleep disorders and gastroenterological disorders, which, by adversely affecting the psyche and increasing inflammation, disturb the metabolism of tryptophan and cause excessive microglial activation, leading to increased susceptibility to pain sensation and depression. Conclusions. Pain therapists should pay close attention to sleep and gastrointestinal disorders in patients with chronic pain and depression.

Depressive symptoms and other negative psychological states relate to ex vivo inflammatory responses differently for men and women: Cross-sectional and longitudinal evidence

An array of negative psychological states - including depressive symptoms, perceived stress, rumination, and negative affect - have been linked to immune function and inflammatory responses. Herein we show evidence of gender-dependent associations between ex vivo lipopolysaccharide (LPS)-stimulated cytokine responses and such psychological states, in both cross-sectional and longitudinal analyses from three annual waves (N = 162 at baseline, 67.3% female). In cross-sectional analyses (at baseline), gender moderated the associations of depressive symptoms (previously reported), perceived stress (B = -0.043, 95%CI [-0.080, -0.015]), rumination (B = -0.500, [-1.015, -0.232]), negative affect (B = -0.020, [-0.020, -0.005]), and positive affect (B = 0.024, [0.008, 0.047]) with LPS-stimulated cytokine responses. In each analysis, negative psychological states were positively associated with LPS-stimulated cytokine responses among men but negatively among women (with associations for positive affect in the opposite direction). In longitudinal analyses (across three annual measurements), similar associations were seen for depressive symptoms (B = -0.024, [-0.059, -0.004]), perceived stress (B = -0.045, [-0.069, -0.024]), and rumination (B = -0.381, [-0.622, -0.120]). These results indicate that gender is a critical factor in associations between a broad array of negative psychological states and inflammatory responses and identify one pathway by which gender may influence psychosomatic health.

Brick by Brick: Building a Transdiagnostic Understanding of Inflammation in Psychiatry

ABSTRACT

Inflammatory phenomena are found in many psychiatric disorders-notably, depression, schizophrenia, and posttraumatic stress disorder. Inflammation has been linked to severity and treatment resistance, and may both contribute to, and result from, the pathophysiology of some psychiatric illnesses. Emerging research suggests that inflammation may contribute to symptom domains of reward, motor processing, and threat reactivity across different psychiatric diagnoses. Reward-processing deficits contribute to motivational impairments in depression and schizophrenia, and motor-processing deficits contribute to psychomotor slowing in both depression and schizophrenia. A number of experimental models and clinical trials suggest that inflammation produces deficits in reward and motor processing through common pathways connecting the cortex and the striatum, which includes the nucleus accumbens, caudate nucleus, and putamen.The observed effects of inflammation on psychiatric disorders may cut across traditional conceptualizations of psychiatric diagnoses. Further study may lead to targeted immunomodulating treatments that address difficult-to-treat symptoms in a number of psychiatric disorders. In this review, we use a Research Domain Criteria framework to discuss proposed mechanisms for inflammation and its effects on the domains of reward processing, psychomotor slowing, and threat reactivity. We also discuss data that support contributing roles of metabolic dysregulation and sex differences on the behavioral outcomes of inflammation. Finally, we discuss ways that future studies can help disentangle this complex topic to yield fruitful results that will help advance the field of psychoneuroimmunology.

Influence of pro-obesogenic dietary habits on stress-induced cognitive alterations in healthy adult volunteers

Stress is a fundamental biological response that can be associated with alterations in cognitive processes. Unhealthy dietary habits are proposed to modulate this effect, notably through their pro-inflammatory potential. This cross-sectional study aimed to evaluate the influence of an obesogenic dietary pattern with inflammatory potential on stress-induced cognitive alterations in healthy volunteers. Fifty healthy adult participants were stratified into two diet groups: obesogenic vs. non-obesogenic, based on their self-reported consumption of fat, sugar, and salt, assessed by the French National Program for Nutrition and Health questionnaire and a food frequency questionnaire. Serum high-sensitive C-reactive protein (hsCRP) was measured as a marker of systemic inflammation using ELISA. Verbal memory and sustained attention were evaluated through the Verbal Recognition Memory (VRM) test and the Rapid Visual Information Processing (RVP) test respectively, from the Cambridge Neuropsychological Test Automated Battery. Assessments were performed before and after exposure to the psychological stressor Trier Social Stress Test (TSST). Stress response was evaluated by subjective stress perception, salivary cortisol, blood pressure, and heart rate. Twenty-two participants (44%) presented an obesogenic diet. Systemic inflammation was significantly higher in the obesogenic diet group (p=0.005). The TSST induced a significant stress response, regardless of dietary habits (Time effect p < 0.001). In the whole sample, exposure to TSST was associated with cognitive changes in the form of impaired performance on the VRM test and overall improved RVP scores. However, the obesogenic diet group exhibited an increased total number of false alarms (Time x Diet: p=0.014) on the RVP test after TSST exposure as well as a greater impairment in immediate verbal recognition on the VRM test (Time x Diet: p=0.002). This effect was not associated with the inflammatory component of the obesogenic diet. These results suggest that an obesogenic diet may sensitize healthy individuals to the detrimental effects of acute stress on cognitive performance.

Similar inflammatory response and conduit artery vascular function between sexes following induced inflammation

NEW FINDINGS

What is the central question of this study? Are there sex differences in vascular function following induced inflammation when oestrogen is typically similar between sexes? What is the main finding and its importance? The present study suggests no sex differences in conduit artery vascular responses to acutely induced inflammation during the low-oestrogen phase of the menstrual cycle in premenopausal women. However, women exhibit lower microvascular function than men. Overall, the results underpin the role of oestrogen in previously observed sex differences and the importance of reporting the phase in the hormonal cycle when women are studied.

ABSTRACT

Sex differences in cardiovascular disease incidence in premenopausal women and age-matched men have been attributed to the cardioprotective influence of oestrogen. However, limited knowledge exists regarding sex differences following acute inflammation when oestrogen concentrations are lower in women. We evaluated sex differences in vascular responses to induced inflammation when oestrogen concentrations are typically lower in women (early follicular phase or placebo phase of hormonal contraception). In 15 women and 14 men, interleukin-6 (IL-6) concentrations and vascular function [via brachial artery flow-mediated dilatation (FMD)] were assessed at baseline (BL) and 24 (24H) and 48 hours (48H) after administration of influenza vaccine. After induction of inflammation, both sexes exhibited an increase in IL-6 concentrations at 24H [mean (SD) BL vs. 24H: women, 0.563 (0.50) vs. 1.141 (0.65) pg/ml; men, 0.385 (0.17) vs. 1.113 (0.69) pg/ml; P < 0.05] that returned to near-baseline concentrations by 48H (BL vs. 48H, P > 0.05). There were no sex differences in FMD, allometrically scaled FMD or IL-6 concentrations at any time point (P > 0.05). Notably, women exhibited significantly lower microvascular function than men at every time point [P < 0.05; reactive hyperaemic area under the curve (in arbitrary units): women, BL 35,512 (14,916), 24H 34,428 (14,292) and 48H 39,467 (13,936); men, BL 61,748 (27,324), 24H 75,028 (29,051) and 48H 59,532 (13,960)]. When oestrogen concentrations are typically lower in women, women exhibit a similar inflammatory response and conduit artery function, but lower microvascular response to reactive hyperaemia, in comparison to age-matched men.

Cytokines profile in neonatal and adult wild-type mice post-injection of U. S. pediatric vaccination schedule

Introduction

A recent study from our laboratory demonstrated a number of neurobehavioral abnormalities in mice colony injected with a mouse-weight equivalent dose of all vaccines that are administered to infants in their first 18 months of life according to the U. S. pediatric vaccination schedule.

Cytokines have been studied extensively as blood immune and inflammatory biomarkers, and their association with neurodevelopmental disorders. Given the importance of cytokines in early neurodevelopment, we aimed to investigate the potential post-administration effects of the U. S. pediatric vaccines on circulatory cytokines in a mouse model.

In the current study, cytokines have been assayed at early and late time points in mice vaccinated early in postnatal life and compared with placebo controls.

Materials and methods

Newborn mouse pups were divided into three groups: i) vaccine (V1), ii) vaccine ​× ​3 (V3) and iii) placebo control. V1 group was injected with mouse weight-equivalent of the current U. S. pediatric vaccine schedule. V3 group was injected with same vaccines but at triple the dose and the placebo control was injected with saline. Pups were also divided according to the sampling age into two main groups: acute- and chronic-phase group. Blood samples were collected at postnatal day (PND) 23, two days following vaccine schedule for the acute-phase group or at 67 weeks post-vaccination for the chronic-phase groups. Fifteen cytokines were analyzed: GM-CSF, IFN-γ, IL-1β, IL-2, IL-4, IL-5, IL-6, IL-9, IL-10, IL-12p70, IL-13, IL-17A, MCP-1, TNF-α, and VEGF-A. Wilcoxon Rank Sum test or unpaired Student's t-test was performed where applicable.

Results

IL-5 levels in plasma were significantly elevated in the V1 and V3 group compared with the control only in the acute-phase group. The elevation of IL-5 levels in the two vaccine groups were significant irrespective of whether the sexes were combined or analyzed separately. Other cytokines (VEGF-A, TNF-α, IL-10, MCP-1, GM-CSF, IL-6, and IL-13) were also impacted, although to a lesser extent and in a sex-dependent manner. In the acute-phase group, females showed a significant increase in IL-10 and MCP-1 levels and a decrease in VEGF-A levels in both V1 and V3 group compared to controls. In the acute-phase, a significant increase in MCP-1 levels in V3 group and CM-CSF levels in V1 and V3 group and decrease in TNF-α levels in V1 group were observed in treated males as compared with controls. In chronic-phase females, levels of VEGF-A in V1 and V3 group, TNF-α in V3 group, and IL-13 in V1 group were significantly decreased in contrast with controls. In chronic-phase males, TNF-α levels were significantly increased in V1 group and IL-6 levels decreased in V3 group in comparison to controls. The changes in levels of most tested cytokines were altered between the early and the late postnatal assays.

Conclusions

IL-5 levels significantly increased in the acute-phase of the treatment in the plasma of both sexes that were subjected to V1 and V3 injections. These increases had diminished by the second test assayed at week 67. These results suggest that a profound, albeit transient, effect on cytokine levels may be induced by the whole vaccine administration supporting our recently published observations regarding the behavioral abnormalities in the same mice. These observations support the view that the administration of whole pediatric vaccines in a neonatal period may impact at least short-term CNS functions in mice.

Acculturation and biological stress markers: A systematic review

BACKGROUND

The association of acculturation with health among immigrant populations is believed to be mediated, in part, by acculturation-related stress and stress biology.

OBJECTIVES

To review and qualitatively synthesize empirical findings on the relationship of acculturation with stress-related inflammatory and endocrine biomarkers and composite allostatic load (AL) scores.

METHODS

A literature search was performed in the PubMed and PsycInfo databases. Article titles, abstracts or full-texts were screened and checked for match with the search criteria. Studies were eligible if they empirically tested the relationship between acculturation and inflammatory/endocrine stress biomarkers or composite AL scores, and were published in the English language.

RESULTS

Among the 41 articles identified as relevant and included in this review, the majority were published after 2010, included adult Hispanic U.S.-based populations, used cross-sectional study designs, operationalized acculturation as a unidimensional construct, and varied considerably in the selection of covariates in the analyses. Acculturation was significantly associated with stress biomarkers in 29 studies, but the direction of effects varied across studies. Specifically, acculturation, operationalized as a higher orientation towards the host culture, was associated with inflammatory biomarkers in 10 of 14 studies, with endocrine stress biomarkers in 12 of 20 studies, and with composite AL scores in 7 of 8 studies. Overall, language-based proxy measures of acculturation were related to higher levels of stress-related inflammatory and endocrine biomarkers and to lower levels of AL scores, whereas nativity-, generation status- and length of stay-based proxy measures of acculturation were related to higher levels of inflammatory biomarkers and AL score.

DISCUSSION

The majority of studies reported associations between measures of acculturation and stress biomarkers, however the directions of effects varied across studies. We suggest this heterogeneity may, in part, be a function of limitations imposed by cross-sectional research designs and unidimensional measures of acculturation measures, and we highlight the need for longitudinal studies and use of multidimensional measures of acculturation to better uncover the biobehavioral mechanisms and pathways linking acculturation with health outcomes.

Inflammation, anxiety, and stress in bipolar disorder and borderline personality disorder: A narrative review

Bipolar disorder (BD) and borderline personality disorder (BPD) are serious and prevalent psychiatric diseases that share common phenomenological characteristics: symptoms (such as anxiety, affective lability or emotion dysregulation), neuroimaging features, risk factors and comorbidities. While several studies have focused on the link between stress and peripheral inflammation in other affective disorders such as anxiety or depression, fewer have explored this relationship in BD and BPD. This review reports on evidence showing an interplay between immune dysregulation, anxiety and stress, and how an altered acute neuroendocrine stress response may exist in these disorders. Moreover, we highlight limitations and confounding factors of these existing studies and discuss multidirectional hypotheses that either suggest inflammation or stress and anxiety as the primum movens in BD and BPD pathophysiology, or inflammation as a consequence of the pathophysiology of these diseases. Untangling these associations and implementing a transdiagnostic approach will have diagnostic, therapeutic and prognostic implications for BD and BPD patients.

Immediate and longitudinal effects of maltreatment on systemic inflammation in young children

Exposure to child maltreatment increases the risk for psychiatric and physical diseases. Inflammation has been proposed as a mechanism through which early adverse experiences become biologically embedded. However, most studies providing evidence for the link between early adverse exposures and inflammation have been retrospective or cross-sectional in design, or did not assess inflammation immediately after maltreatment in young children. In the present study we investigated the association between childhood maltreatment and salivary C-reactive protein (CRP) concentrations in a population of N = 173 children, 3-5 years of age, who were recruited in the immediate aftermath of maltreatment and followed-up longitudinally every 6 months over a period of 2 years. We found that the association between maltreatment and CRP concentrations was significantly moderated by child sex, such that in girls, CRP concentrations were higher in the maltreated compared to the control group, and this difference was stable across the 2-year follow-up-period, while in boys, there was no association between maltreatment and CRP. Our findings suggest that the effect of maltreatment on inflammation may already emerge right after exposure at a very young age in girls and manifest over time. Our study provides important evidence for the development of personalized, early interventions strategies targeting the early-life period.

Sex Differences in the Inflammatory Consequences of Stress: Implications for Pharmacotherapy

Women are at significantly greater risk of developing stress-related disorders such as depression. The increased risk begins during puberty and continues throughout life until menopause, suggesting a role for ovarian hormones in this increased susceptibility. Importantly, inflammation has been gaining momentum in its role in the pathogenesis of depression. Herein, clinical and preclinical studies have been reviewed to better understand how sex differences within the immune system may contribute to exaggerated risk of depression in females. First, studies that investigate the ability of psychologic stress episodes to engage the inflammatory systems both in the brain and periphery are reviewed with a special focus on sex-specific effects. Moreover, studies are discussed that identify whether imbalanced inflammatory milieu contributes to the development of depression in males versus females and whether these effects are regulated by estradiol. Importantly, we propose a locus coeruleus-norepinephrine-cytokine circuit as a conduit through which stress could increase stress susceptibly in females. Finally, the anti-inflammatory capacity of traditional and nontraditional antidepressants is investigated, with the goal of providing a better understanding of pharmacotherapeutics to enhance strategies to personalize antidepressant treatments between the sexes. The studies reviewed herein strongly support the need for further studies to elucidate whether females are especially sensitive to anti-inflammatory compounds as adjuvants to traditional therapies. SIGNIFICANCE STATEMENT: Women have hve an increased risk of developing stress-related disorders such as depression. In this review, literature from clinical and preclinical studies are integrated to define sex differences in stress-induced inflammatory responses as a potential source for the etiology of sex differences in depressive disorders. Moreover, the anti-inflammatory capacity of traditional and nontraditional antidepressants is reviewed to inform on potential pharmacotherapeutic strategies to personalize antidepressant therapy in a sex-dependent manner.

IL-6 Response to Psychosocial Stress Predicts 12-month Changes in Cardiometabolic Biomarkers in Perimenopausal Women

OBJECTIVE

Cardiometabolic diseases are the number one cause of mortality, accounting for over one third of all deaths in the United States. Cardiometabolic risk further increases with psychosocial stress exposure and during menopausal transition in women. Because disease risk and stress burden are associated with aberrant immune signaling, we hypothesized that responses of interleukin-6 (IL-6) to psychosocial stress may predict longitudinal cardiometabolic outcomes in perimenopausal women.

METHODS

We conducted post hoc analyses in 151 perimenopausal or early postmenopausal women participants in a previously completed study. At study onset, participants underwent the Trier Social Stress Test (TSST), and plasma IL-6 was measured repeatedly before and during the 1 hour post-TSST. Subsequently, participants were randomly assigned to either hormonal treatment (HT) or placebo and followed for 12 months to determine longitudinal changes in cardiometabolic biomarkers.

RESULTS

Greater IL-6 reactivity to stress, measured with baseline-adjusted area under the curve, predicted 12-month decrease in flow-mediated dilatation of the brachial artery (P = 0.0005), a measure of endothelial-dependent vascular function, but not in endothelial-independent function measured with nitroglycerin-mediated dilatation (P = 0.17). Greater baseline IL-6 levels predicted 12-month increase in insulin resistance based on the homeostatic model assessment of insulin resistance score (P = 0.0045) and in the number of criteria met for metabolic syndrome (P = 0.0008). These predictions were not moderated by HT.

CONCLUSIONS

Greater baseline IL-6 levels as well as its reactivity to stress may predict worsening in distinct cardiometabolic biomarkers as women transition to menopause. Interleukin-6 reactivity predicts decline in endothelial-dependent vascular function, whereas baseline IL-6 presages accumulation of metabolic risk.

A double-hit of stress and low-grade inflammation on functional brain network mediates posttraumatic stress symptoms

Growing evidence indicates a reciprocal relationship between low-grade systemic inflammation and stress exposure towards increased vulnerability to neuropsychiatric disorders, including posttraumatic stress disorder (PTSD). However, the neural correlates of this reciprocity and their influence on the subsequent development of PTSD are largely unknown. Here we investigated alterations in functional connectivity among brain networks related to low-grade inflammation and stress exposure using two large independent data sets. Functional couplings among the higher-order cognitive network system including the salience, default mode, and central executive networks were reduced in association with low-grade inflammation and stress exposure. This reduced functional coupling may also be related to subsequent posttraumatic stress symptom severity. The current findings propose functional couplings among the higher-order cognitive network system as neural correlates of low-grade inflammation and stress exposure, and suggest that low-grade inflammation, alongside with stress, may render individuals more vulnerable to PTSD.

Mediation of the Acute Stress Response by the Skeleton

We hypothesized that bone evolved, in part, to enhance the ability of bony vertebrates to escape danger in the wild. In support of this notion, we show here that a bone-derived signal is necessary to develop an acute stress response (ASR). Indeed, exposure to various types of stressors in mice, rats (rodents), and humans leads to a rapid and selective surge of circulating bioactive osteocalcin because stressors favor the uptake by osteoblasts of glutamate, which prevents inactivation of osteocalcin prior to its secretion. Osteocalcin permits manifestations of the ASR to unfold by signaling in post-synaptic parasympathetic neurons to inhibit their activity, thereby leaving the sympathetic tone unopposed. Like wild-type animals, adrenalectomized rodents and adrenal-insufficient patients can develop an ASR, and genetic studies suggest that this is due to their high circulating osteocalcin levels. We propose that osteocalcin defines a bony-vertebrate-specific endocrine mediation of the ASR.

Association between chronotype and body mass index: The role of C-reactive protein and the cortisol response to stress

BACKGROUND

Chronotype influences several physiological systems, including the immune system and the hypothalamus-pituitary-adrenal (HPA)-axis. Previous research has shown that evening chronotype is associated with adverse metabolic health outcomes and obesity. However, the exact mechanisms underlying the observed differences in metabolic function between "morning" and "evening" types remain to be explored.

OBJECTIVE

To investigate the relationship of chronotype with inflammatory and neuroendocrine stress markers and to explore their mediating and moderating roles in the association between chronotype and body mass index (BMI).

METHODS

Twenty-eight healthy young adults (50% women), mean age 23.8 ± 3.3 (SD) years, underwent a standardized laboratory stress test (Trier Social Stress Test, TSST). Concentrations of plasma C-reactive protein (CRP) at baseline and of salivary cortisol before and after the onset of the stressor were analyzed. Heart rate was measured continuously. Chronotype was assessed with the Morningness-Eveningness Questionnaire (MEQ).

RESULTS

Lower MEQ scores (i.e. evening tendency) were associated with higher BMI (r = -.40, p < .05), elevated CRP concentrations (r = -.42, p < .05) and higher cortisol responses to acute stress (r = -.53, p < .01). The relationship between MEQ score and BMI was mediated by CRP concentrations (b = -0.03, CI 95%: -0.08 to -0.007, p < .05). In addition, we observed a moderating effect of the cortisol stress response on this mediated relationship (b = 0.005, CI 95%: 0.0002 to 0.01, p < .05), such that the mediated relationship was stronger in individuals with a higher cortisol response.

CONCLUSION

Enhanced pro-inflammatory state and a higher cortisol response to stress may underlie the effect of evening chronotype on obesity risk and adverse metabolic health outcomes.

Sex-specific roles of cellular inflammation and cardiometabolism in obesity-associated depressive symptomatology

BACKGROUND

Obesity and depression are complex conditions with stronger comorbid relationships among women than men. Inflammation and cardiometabolic dysfunction are likely mechanistic candidates for increased depression risk, and their prevalence differs by sex. Whether these relationships extend to depressive symptoms is poorly understood. Therefore, we analyzed sex in associations between inflammation and metabolic syndrome (MetS) criteria on depressive symptomatology. Specifically, we examined whether sex positively moderates the relationship between depressive symptoms and inflammation among women, and whether MetS has parallel effects among men.

METHODS

Depressive symptoms, MetS, and inflammation were assessed in 129 otherwise healthy adults. Depressive symptoms were assessed using Beck Depression Inventory (BDI-Ia). Monocyte inflammation regulation (BARIC) was quantified using flow cytometry measurement of TNF-α suppression by β-agonist. Moderation effects of sex on associations between BARIC, MetS criteria, and BDI were estimated using two-way ANOVA and linear regression, adjusting for BMI, and by sex subgroup analyses.

RESULTS

Obese individuals reported more depressive symptoms. Sex did not formally moderate this relationship, though BDI scores tended to differ by BMI among women, but not men, in subgroup analysis. Poorer inflammation control and higher MetS criteria were correlated with somatic depressive symptoms. Sex moderated associations between MetS criteria and somatic symptoms; among men, MetS criteria predicted somatic symptoms, not among women. Subgroup analysis further indicated that poorer inflammation control tended to be associated with higher somatic symptoms in women.

CONCLUSIONS

These results indicate that obesity-related inflammation and MetS factors have sex-specific effects on depressive symptoms in a non-clinical population. Although pathophysiological mechanisms underlying sex differences remain to be elucidated, our findings suggest that distinct vulnerabilities to depressive symptoms exist between women and men, and highlight the need to consider sex as a key biological variable in obesity-depression relationships. Future clinical studies on comorbid obesity and depression should account for sex, which may optimize therapeutic strategies.

Individual differences in inflammatory and oxidative mechanisms of stress-related mood disorders

Emotional stress leads to the development of peripheral disorders and is recognized as a modifiable risk factor for psychiatric disorders, particularly depression and anxiety. However, not all individuals develop the negative consequences of emotional stress due to different stress coping strategies and resilience to stressful stimuli. In this review, we discuss individual differences in coping styles and the potential mechanisms that contribute to individual vulnerability to stress, such as parameters of the immune system and oxidative state. Initial differences in inflammatory and oxidative processes determine resistance to stress and stress-related disorders via the alteration of neurotransmitter content in the brain and biological fluids. Differences in coping styles may serve as possible predictors of resistance to stress and stress-related disorders, even before stressful conditions. The investigation of natural variabilities in stress resilience may allow the development of new methods for preventive medicine and the personalized treatment of stress-related conditions.

Predictors of ccf-mtDNA reactivity to acute psychological stress identified using machine learning classifiers: A proof-of-concept

OBJECTIVE

We have previously found that acute psychological stress may affect mitochondria and trigger an increase in serum mitochondrial DNA, known as circulating cell-free mtDNA (ccf-mtDNA). Similar to other stress reactivity measures, there are substantial unexplained inter-individual differences in the magnitude of ccf-mtDNA reactivity, as well as within-person differences across different occasions of testing. Here, we sought to identify psychological and physiological predictors of ccf-mtDNA reactivity using machine learning-based multivariate classifiers.

METHOD

We used data from serum ccf-mtDNA concentration measured pre- and post-stress in 46 healthy midlife adults tested on two separate occasions. To identify variables predicting the magnitude of ccf-mtDNA reactivity, two multivariate classification models, partial least-squares discriminant analysis (PLS-DA) and random forest (RF), were trained to discriminate between high and low ccf-mtDNA responders. Potential predictors used in the models included state variables such as physiological measures and affective states, and trait variables such as sex and personality measures. Variables identified across both models were considered to be predictors of ccf-mtDNA reactivity and selected for downstream analyses.

RESULTS

Identified predictors were significantly enriched for state over trait measures (X2 = 7.03; p = 0.008) and for physiological over psychological measures (X2 = 4.36; p = 0.04). High responders were more likely to be male (X2 = 26.95; p < 0.001) and differed from low-responders on baseline cardiovascular and autonomic measures, and on stress-induced reduction in fatigue (Cohen's d = 0.38-0.73). These group-level findings also accurately accounted for within-person differences in 90% of cases.

CONCLUSION

These results suggest that acute cardiovascular and psychological indices, rather than stable individual traits, predict stress-induced ccf-mtDNA reactivity. This work provides a proof-of-concept that machine learning approaches can be used to explore determinants of inter-individual and within-person differences in stress psychophysiology.

Acute psychological stress increases serum circulating cell-free mitochondrial DNA

Intrinsic biological mechanisms transduce psychological stress into physiological adaptation that requires energy, but the role of mitochondria and mitochondrial DNA (mtDNA) in this process has not been defined in humans. Here, we show that similar to physical injury, exposure to psychological stress increases serum circulating cell-free mtDNA (ccf-mtDNA) levels. Healthy midlife adults exposed on two separate occasions to a brief psychological challenge exhibited a 2-3-fold increase in ccf-mtDNA, with no change in ccf-nuclear DNA levels, establishing the magnitude and specificity for ccf-mtDNA reactivity. In cell-based studies, we show that glucocorticoid signaling - a consequence of psychological stress in humans - is sufficient to induce mtDNA extrusion in a time frame consistent with stress-induced ccf-mtDNA increase. Collectively, these findings provide evidence that acute psychological stress induces ccf-mtDNA and implicate neuroendocrine signaling as a potential trigger for ccf-mtDNA release. Further controlled work is needed to confirm that observed increases in ccf-mtDNA result from stress exposure and to determine the functional significance of this effect.

Gender-Specific Differences in Concentrations of Biochemical Parameters in Persons over the Age of 90

The ageing process is a phenomenon leading to an emergence of a web of interrelated biological processes producing significant changes in the human body. The aim of the paper was to analyse gender-specific differences with regard to selected biochemical parameters in longevity. The study was conducted in Poland in 2017. The study population comprised of long-lived individuals, both living at home and staying at residential care homes. There were 90 people of both genders (69 women and 21 men) aged between 90 and 103 years (mean = 92.36; SD = 2.98). The biochemical markers of longevity in the studied patients were identified by assessing their pro-inflammatory and anti-inflammatory status in various metabolic aspects. The analysis of biochemical variables revealed numerous statistically significant differences, both in the study group as a whole and between the genders. The ageing process is extremely complex, but understanding it will allow for a real intervention in life extension. Research into the processes involved in ageing and longevity will enable a better understanding of the mechanisms responsible for them, and to enjoy those processes in good health.

Links Between Stress, Sleep, and Inflammation: Are there Sex Differences?

PURPOSE OF REVIEW

Inflammation has emerged as an important biological process in the development of many age-related diseases that occur at different frequencies in men and women. The aim of this review was to examine the current evidence linking stress and sleep with inflammation with a focus on sex differences.

RECENT FINDINGS

Psychosocial stress that occurs either acutely or chronically is associated with elevated levels of systemic inflammation. While not as robust, insufficient sleep, particularly sleep disturbances, appears to be associated with higher levels of inflammatory activity as well. In several contexts, associations of stress and insufficient sleep with inflammation appear stronger in women than in men. However, this should be interpreted with caution as few studies test for sex differences. Stress and poor sleep often predict elevations in systemic inflammation. While there is some evidence that these associations are stronger in women, findings are largely mixed and more systematic investigations of sex differences in future studies are warranted.

Sex differences in interleukin-6 stress responses in people with Type 2 diabetes

People with Type 2 diabetes (T2D) show dysregulated inflammatory responses to acute stress, but the effect of sex on inflammatory responses in T2D remains unclear. The purpose of this study was to investigate differences in interleukin (IL)-6 stress responses between older men and women with T2D. One hundred and twenty-one people (76 men; mean age = 64.09, SD = 7.35, 45 women; mean age = 63.20, SD = 6.70) with doctor-verified T2D took part in this laboratory-based stress testing study. Participants carried out acute mental stress tasks, and blood was sampled at baseline, immediately poststress, 45 min poststress, and 75 min poststress to detect plasma IL-6 concentrations. IL-6 change scores were computed as the difference between the baseline measurement and the three time points poststress. Main effects and interactions were tested using mixed model analysis of covariance. We found a significant main effect of time on IL-6 levels, and a significant Sex × Time interaction. In adjusted analyses including the three change scores and all the covariates, the significant Sex × Time interaction was maintained; IL-6 responses were greater in women at 45 and 75 min poststress compared with men, adjusting for age, body mass index, smoking, household income, glycated hemoglobin, oral antidiabetic medication, insulin/other injectable antidiabetic medication, depressive symptoms, and time of day of testing. Different inflammatory stress response pathways are present in men and women with T2D, with women producing larger IL-6 increases. The long-term implications of these differences need to be elucidated in future studies.

Gastric responses to acute psychological stress in climacteric women: a pilot study

OBJECTIVE

Women exhibit reduced ovarian sex hormones during the menopausal period that result in well-known physical and psychological symptoms. However, symptoms related to gastric motility (GM) have not been thoroughly investigated. We hypothesized that stress response gastric motility (SRGM) is lower in postmenopausal (PM) and perimenopausal (PERIM) women than in premenopausal (PREM) women. Estrogenic decline leads to neuroendocrine changes in different areas of the brain. These changes can result in hypothalamic vasomotor symptoms, disorders in eating behaviours, and altered blood pressure, in addition to psychological disorders such as stress, anxiety, depression, and irritability related to alterations in the limbic system.

METHODS

In this pilot study, 55 PREM, PERIM, and PM women were clinically evaluated using the Nowack stress profile (SP) and State-Trait Anxiety Inventory (STAI). GM was assessed via electrical bioimpedance using two psychological stress tests (Stroop and Raven tests).

RESULTS

Basal SP and STAI-anxiety test scores were similar among the three groups of women (P > 0.05). PERIM women had lower GM in the basal state (P < 0.05) than did other women. PREM and PM women had significantly decreased GM during the stress tests (P < 0.05). However, PERIM did not exhibit GM changes during stress tests (P > 0.05).

CONCLUSION

Changes in sex hormones during PERIM may affect GM and SRGM.

Functional neuroanatomy of peripheral inflammatory physiology: A meta-analysis of human neuroimaging studies

Communication between the brain and peripheral mediators of systemic inflammation is implicated in numerous psychological, behavioral, and physiological processes. Functional neuroimaging studies have identified brain regions that associate with peripheral inflammation in humans, yet there are open questions about the consistency, specificity, and network characteristics of these findings. The present systematic review provides a meta-analysis to address these questions. Multilevel kernel density analysis of 24 studies (37 statistical maps; 264 coordinates; 457 participants) revealed consistent effects in the amygdala, hippocampus, hypothalamus, striatum, insula, midbrain, and brainstem, as well as prefrontal and temporal cortices. Effects in some regions were specific to particular study designs and tasks. Spatial pattern analysis revealed significant overlap of reported effects with limbic, default mode, ventral attention, and corticostriatal networks, and co-activation analyses revealed functional ensembles encompassing the prefrontal cortex, insula, and midbrain/brainstem. Together, these results characterize brain regions and networks associated with peripheral inflammation in humans, and they provide a functional neuroanatomical reference point for future neuroimaging studies on brain-body interactions.

Cytokine secretion responsiveness of lymphomonocytes following cortisol cell exposure: Sex differences

The stress hormone cortisol has been recognized as a coordinator of immune response. However, its different ability to modulate the release of inflammatory mediators in males and females has not been clarified yet. Indeed, the dissection of cortisol specific actions may be difficult due to the complex hormonal and physio-pathological individual status. Herein, the release of inflammatory mediators following increasing cortisol concentrations was investigated in an in vitro model of primary human male and female lymphomonocytes. The use of a defined cellular model to assess sex differences in inflammatory cytokine secretion could be useful to exclude the effects of divergent and fluctuating sex hormone levels occurring in vivo. Herein, the cells were challenged with cortisol concentrations resembling the plasma levels achieving in physiological and stressful conditions. The production of cytokines and other molecules involved in inflammatory process was determined. In basal conditions, male cells presented higher levels of some pro-inflammatory molecules (NF-kB and IDO-1 mRNAs, IL-6 and kynurenine) than female cells. Following cortisol exposure, the levels of the pro-inflammatory cytokines, IL-6 and IL-8, were increased in male cells. Conversely, in female cells IL-6 release was unchanged and IL-8 levels were decreased. Anti-inflammatory cytokines, IL-4 and IL-10, did not change in male cells and increased in female cells. Interestingly, kynurenine levels were higher in female cells than in male cells following cortisol stimulus. These results highlighted that cortisol differently affects male and female lymphomonocytes, shifting the cytokine release in favour of a pro-inflammatory pattern in male cells and an anti-inflammatory secretion profile in female cells, opening the way to study the influences of other stressful factors involved in the neurohumoral changes occurring in the response to stress conditions.

Sex differences in the neuro-immune consequences of stress: Focus on depression and anxiety

Women appear to be more vulnerable to the depressogenic effects of inflammation than men. Chronic stress, one of the most pertinent risk factors of depression and anxiety, is known to induce behavioral and affective-like deficits via neuroimmune alterations including activation of the brain's immune cells, pro-inflammatory cytokine expression, and subsequent changes in neurotransmission and synaptic plasticity within stress-related neural circuitry. Despite well-established sexual dimorphisms in the stress response, immunity, and prevalence of stress-linked psychiatric illnesses, much of current research investigating the neuroimmune impact of stress remains exclusively focused on male subjects. We summarize and evaluate here the available data regarding sex differences in the neuro-immune consequences of stress, and some of the physiological factors contributing to these differences. Furthermore, we discuss the extent to which sex differences in stress-related neuroinflammation can account for the overall female bias in stress-linked psychiatric disorders including major depressive disorder and anxiety disorders. The currently available evidence from rodent studies does not unequivocally support the peripheral inflammatory changes seen in women following stress. Replication of many recent findings in stress-related neuroinflammation in female subjects is necessary in order to build a framework in which we can assess the extent to which sex differences in stress-related inflammation contribute to the overall female bias in stress-related affective disorders.

The very low-frequency band of heart rate variability represents the slow recovery component after a mental stress task

The very low-frequency (VLF) band of heart rate variability (HRV) has different characteristics compared with other HRV components. Here we investigated differences in HRV changes after a mental stress task. After the task, the high-frequency (HF) band and ratio of high- to low-frequency bands (LF/HF) immediately returned to baseline. We evaluated the characteristics of VLF band changes after a mental stress task. We hypothesized that the VLF band decreases during the Stroop color word task and there would be a delayed recovery for 2 h after the task (i.e., the VLF change would exhibit a “slow recovery”).

Nineteen healthy, young subjects were instructed to rest for 10 min, followed by a Stroop color word task for 20 min. After the task, the subjects were instructed to rest for 120 min. For all subjects, R-R interval data were collected; analysis was performed for VLF, HF, and LF/HF ratio. HRV during the rest time and each 15-min interval of the recovery time were compared. An analysis of the covariance was performed to adjust for the HF band and LF/HF ratio as confounding variables of the VLF component.

HF and VLF bands significantly decreased and the LF/HF ratio significantly increased during the task compared with those during rest time. During recovery, the VLF band was significantly decreased compared with the rest time. After the task, the HF band and LF/HF ratio immediately returned to baseline and were not significantly different from the resting values. After adjusting for HF and LF/HF ratio, the VLF band had significantly decreased compared with that during rest.

The VLF band is the “slow recovery” component and the HF band and LF/HF ratio are the “quick recovery” components of HRV. This VLF characteristic may clarify the unexplained association of the VLF band in cardiovascular disease prevention.

The effects of acute psychological stress on circulating and stimulated inflammatory markers: A systematic review and meta-analysis

Inflammatory reactivity to acute laboratory stress is thought to reflect individual differences in responsivity to environmental stressors and may confer future health risk. To characterize this response, we conducted a meta-analysis of 34 studies that measured circulating inflammatory markers and 15 studies that measured stimulated production of inflammatory markers before and after exposure to laboratory challenge. Results showed significant stress-related increases in circulating interleukin (IL)-1β (d=0.66, p<0.001), IL-6 (d=0.35, p<0.001), IL-10 (d=0.69, p<0.001), and tumor necrosis factor(TNF)-α (d=0.28, p<0.001), but not IL-1ra, IL-2, interferon-γ, or C-reactive protein. There were sufficient data to assess the time course of IL-6, IL-1β, and TNF-α reactivity. IL-6 increased from baseline to measures taken 40-50, 60-75, 90, and 120min following stress, with the largest effect at 90min post-stress (d=0.70, p<0.001). IL-1β increased from baseline to 20-30, 40-50, and 60-70min following stress, with the largest effect between 40 and 50min post-stress (d=0.73, p=0.02). For TNF-α, there was a significant increase from baseline to 31-50min post stress (d=0.44, p=0.01), but not at later times. There was no difference in magnitude of IL-6 reactivity as a function of type of stress (social-evaluative versus other). For stimulated inflammatory markers, results showed stress-related increases in IL-1β when measured 20-120min post-stress (d=1.09, p<0.001), and in IL-4 and interferon-γ when measured 0-10min post stressor (d=-0.42, p<0.001 and d=0.47, p<0.001). These results extend findings from a prior meta-analysis (Steptoe et al., 2007) to show reliable increases in circulating IL-6, IL-1β, IL-10 and TNF-α and stimulated IL-1β, IL-4 and interferon-γ in response to acute stress. It is possible that these responses contribute to associations between exposure to life challenges and vulnerability to inflammatory disease.

Post-menopausal Women Exhibit Greater Interleukin-6 Responses to Mental Stress Than Older Men

BACKGROUND

Acute stress triggers innate immune responses and elevation in circulating cytokines including interleukin-6 (IL-6). The effect of sex on IL-6 responses remains unclear due to important limitations of previous studies.

PURPOSE

The purpose of this study was to examine sex differences in IL-6 responses to mental stress in a healthy, older (post-menopausal) sample accounting for several moderating factors.

METHODS

Five hundred six participants (62.9 ± 5.60 years, 55 % male) underwent 10 min of mental stress consisting of mirror tracing and Stroop task. Blood was sampled at baseline, after stress, and 45 and 75 min post-stress, and assayed using a high sensitivity kit. IL-6 reactivity was computed as the mean difference between baseline and 45 min and between baseline and 75 min post-stress. Main effects and interactions were examined using ANCOVA models.

RESULTS

There was a main effect of time for the IL-6 response (F 3,1512 = 201.57, p = <.0001) and a sex by time interaction (F 3,1512 = 17.07, p = <.001). In multivariate adjusted analyses, IL-6 reactivity was significantly greater in females at 45 min (M = 0.37 ± 0.04 vs. 0.20 ± 0.03 pg/mL, p = .01) and at 75 min (M = 0.57 ± 0.05 vs. 0.31 ± 0.05 pg/mL, p = .004) post-stress compared to males. Results were independent of age, adiposity, socioeconomic position, depression, smoking and alcohol consumption, physical activity, statin use, testing time, task appraisals, hormone replacement, and baseline IL-6. Other significant predictors of IL-6 reactivity were lower household wealth, afternoon testing, and baseline IL-6.

CONCLUSIONS

Healthy, post-menopausal females exhibit substantially greater IL-6 responses to acute stress. Inflammatory responses if sustained over time may have clinical implications for the development and maintenance of inflammatory-related conditions prevalent in older women.

Trait Hostility and Acute Inflammatory Responses to Stress in the Laboratory

Hostility has been associated with higher basal levels of inflammation. The present study evaluated the association of hostility with acute stress-induced changes in inflammatory activity. One hundred and ninety-nine healthy men and women, aged 19–64 years, were exposed to a stress protocol involving four interpersonal stressors. Participants completed the Cook-Medley Hostility questionnaire and provided two blood samples for the measurement of inflammatory biomarkers (CRP, Il-6, MPO, TNF-α, MCP-1, Il-8, Il-10, and Il-18), prior to and following exposure to a standardized stress protocol. In univariate analyses, hostility was associated with significantly higher TNF-α, but lower Il-8 and Il-18 values post-stress, though only Il-8 remained significant after controlling for baseline differences. In multivariate analyses, a significant Age by Hostility interaction emerged for Il-6, while sex moderated the relation between hostility and Il-10 reactivity. Following stress, hostility was associated with greater pro-inflammatory Il-6 activity among younger individuals and to decreased anti-inflammatory Il-10 activity in women. Future research is needed to replicate these findings and to evaluate their implication for disease.

Maternal distress and child neuroendocrine and immune regulation

RATIONALE

Neuroendocrine-immune regulation is essential for maintaining health. Early-life adversity may cause dysregulation in the neuroendocrine-immune network through repeated activation of the stress response, thereby increasing disease risk.

OBJECTIVE

This paper examined the extent to which maternal psychological well-being moderates neuroendocrine-immune relations in children.

METHODS

We used data from a laboratory-based study of mothers and their five-year old children (n = 125 mother-child pairs) conducted from 2011 to 2013 in Baltimore, Maryland. Child saliva was assayed for markers of immune function (i.e., cytokines: interleukin [IL]-1β, IL-6, IL-8, tumor necrosis factor alpha [TNF-α]) and hypothalamic-pituitary-adrenal activity (i.e., cortisol). A composite score for depressive symptoms, anxiety, and parenting stress characterized maternal psychological distress. Multilevel mixed models examined the relationship between maternal psychological well-being and child neuroendocrine-immune relations.

RESULTS

Significant cytokine × maternal distress interactions indicated that as maternal distress increased, expected inverse cytokine-cortisol relations within children became weaker for IL-1β, IL-6, and TNF-α. Sex-stratified models revealed that these interactions were only significant among girls. Among boys, there were inverse cytokine-cortisol relations for all cytokines, and, while in the same direction as observed among girls, the cytokine × maternal distress interactions were non-significant.

CONCLUSION

The findings suggest that maternal distress is associated with child neuroendocrine-immune relations in saliva and may alter the sensitivity of inflammatory immune processes to cortisol's inhibitory effects. This desensitization may place the child at risk for inflammatory diseases. The findings support efforts for the early detection and treatment of at-risk mothers to protect maternal and child health and well-being.

Physiologic variability at the verge of systemic inflammation: multiscale entropy of heart rate variability is affected by very low doses of endotoxin

INTRODUCTION

Human injury or infection induces systemic inflammation with characteristic neuroendocrine responses. Fluctuations in autonomic function during inflammation are reflected by beat-to-beat variation in heart rate, termed heart rate variability (HRV). In the present study, we determine threshold doses of endotoxin needed to induce observable changes in markers of systemic inflammation, investigate whether metrics of HRV exhibit a differing threshold dose from other inflammatory markers, and investigate the size of data sets required for meaningful use of multiscale entropy (MSE) analysis of HRV.

METHODS

Healthy human volunteers (n = 25) were randomized to receive placebo (normal saline) or endotoxin/lipopolysaccharide (LPS): 0.1, 0.25, 0.5, 1.0, or 2.0 ng/kg administered intravenously. Vital signs were recorded every 30 min for 6 h and then at 9, 12, and 24 h after LPS. Blood samples were drawn at specific time points for cytokine measurements. Heart rate variability analysis was performed using electrocardiogram epochs of 5 min. Multiscale entropy for HRV was calculated for all dose groups to scale factor 40.

RESULTS

The lowest significant threshold dose was noted in core temperature at 0.25 ng/kg. Endogenous tumor necrosis factor α and interleukin 6 were significantly responsive at the next dosage level (0.5 ng/kg) along with elevations in circulating leukocytes and heart rate. Responses were exaggerated at higher doses (1 and 2 ng/kg). Time domain and frequency domain HRV metrics similarly suggested a threshold dose, differing from placebo at 1.0 and 2.0 ng/kg, below which no clear pattern in response was evident. By applying repeated-measures analysis of variance across scale factors, a significant decrease in MSE was seen at 1.0 and 2.0 ng/kg by 2 h after exposure to LPS. Although not statistically significant below 1.0 ng/kg, MSE unexpectedly decreased across all groups in an orderly dose-response pattern not seen in the other outcomes.

CONCLUSIONS

By using repeated-measures analysis of variance across scale factors, MSE can detect autonomic change after LPS challenge in a group of 25 subjects using electrocardiogram epochs of only 5 min and entropy analysis to scale factor of only 40, potentially facilitating MSE's wider use as a research tool or bedside monitor. Traditional markers of inflammation generally exhibit threshold dose behavior. In contrast, MSE's apparent continuous dose-response pattern, although not statistically verifiable in this study, suggests a potential subclinical harbinger of infectious or other insult. The possible derangement of autonomic complexity prior to or independent of the cytokine surge cannot be ruled out. Future investigation should focus on confirmation of overt inflammation following observed decreases in MSE in a clinical setting.

Effects of insomnia disorder and knee osteoarthritis on resting and pain-evoked inflammatory markers

Osteoarthritis is the most prevalent arthritic condition. Systemic inflammatory cytokines appear to have an important role in the onset and maintenance of the disease. Sleep disturbances are prevalent in osteoarthritis and associated with alterations in systemic inflammatory cytokines, suggesting a common pathophysiology across these conditions. A comparative investigation of the effects of insomnia disorder and osteoarthritis on pain-evoked cytokine responses has yet to be undertaken. We examined the influence of symptomatic knee osteoarthritis and insomnia disorder on resting C-reactive protein (CRP), interleukin (IL)-6, and IL-10 levels, and pain-evoked IL-6 and IL-10 responses. Participants were N=117 older adults (mean age=59.7years; 61.8% women) rigorously evaluated for knee osteoarthritis and insomnia disorder using established diagnostic guidelines. Results revealed no association of osteoarthritis or insomnia disorder with CRP. Resting IL-6 was greater in osteoarthritis participants versus those without osteoarthritis, although this association was largely attributable to BMI. IL-10 was highest among participants with osteoarthritis or insomnia disorder. Growth curve modeling revealed that participants with insomnia disorder had greater pain-evoked IL-6 responses than participants without insomnia disorder or osteoarthritis. These findings highlight the utility of laboratory pain testing methods for understanding individual differences in inflammatory cytokines. Moreover, our findings provide evidence for amplified pain-evoked pro-inflammatory cytokine reactivity among older adults with clinically diagnosed insomnia disorder, even after controlling for individual differences in BMI and age. Additional research will be required determine whether an amplified pain-related cytokine response contributes to OA, and possibly other age-related disease, associated with insomnia disorder.

Acute aerobic exercise mediates G protein-coupled receptor kinase 2 expression in human PBMCs

AIMS

G protein-coupled receptor kinase 2 (GRK2), a cytosolic enzyme desensitizing G protein-couple receptors (e.g., β-adrenergic receptors [β-ARs]), is involved in regulation of hypertension, congestive heart failure, and inflammatory response. Since cellular GRK2 levels change quickly in response to exogenous/endogenous stimuli, this study examined whether GRK2 levels in human peripheral blood mononuclear cells (PBMCs) would increase during acute aerobic exercise and be associated with plasma IL-6 and cardiorespiratory fitness levels.

MAIN METHODS

Eighteen subjects (8 men and 10 women), ages 18 to 30 years, were recruited to perform a 30-minute bout of acute aerobic exercise at 75% VO2max.

KEY FINDINGS

Our results demonstrated that women exhibited significantly greater exercise-induced GRK2 expression in PBMCs compared to men. IL-6 modulation is independent of GRK2 expression. Furthermore, the percent change in GRK2 expression was negatively correlated with cardiorespiratory fitness levels (relative VO2max), but not plasma IL-6.

SIGNIFICANCE

Acute aerobic exercise induces a greater GRK2 expression in women than men, while increased cardiorespiratory fitness is associated with exercise-induced GRK2 expression in PBMCs. Gender could be a contributor to regulate this GRK2 responsiveness to acute aerobic exercise.

Differences of plasma IL-1 and TNF-α in healthy Chinese Population

Pleiotropic proinflammatory cytokines, interleukin- 1 (IL-1) and tumor necrosis factor-α (TNF-α), involved in the regulations of various immune responses, inflammatory processes and hematopoiesis. In the present study, the expression levels of IL-1 and TNF-α were detected by enzyme-linked immunosorbent assay (ELISA). Following the cytokine blockade as a successful clinical therapy for autoimmune diseases such as rheumatoid arthritis, the patients are more susceptible to a variety of opportunistic infections. IL-1 and TNF-α may be useful predictive biomarkers of diseases and offer potential targets for therapeutic intervention of inflammatory diseases. However, our results showed that the plasma IL-1 level was significantly higher in women compared to men (69.5 ± 19.8 pg/ml in men and 80.1 ± 19.5 pg/ml in women, respectively); the plasma levels of TNF-α were higher in men than women (20.8 ± 4.9 pg/ml and 18.7 ± 7.1 pg/ml, respectively). The significant gender difference of plasma interleukin-1 (IL-1) and TNF-α levels present in healthy adults in Jiangsu Province, China (P=0.002 and P=0.015, respectively), and may be as a hint for sex differences of susceptibility to many diseases and elementary immune response.

Affective reactivity to daily stressors is associated with elevated inflammation

OBJECTIVE

Inflammation increases the risk of chronic diseases, but the links between emotional responses to daily events and inflammation are unknown. We examined individual differences in affective reactivity to daily stressors (i.e., changes in positive and negative affect in response to stressors) as predictors of inflammatory markers interleukin-6 (IL-6) and C-reactive protein (CRP).

METHODS

A cross-sectional sample of 872 adults from the National Study of Daily Experiences (substudy of Midlife in the United States II) reported daily stressors and affect during telephone interviews for 8 days. Blood samples were obtained at a separate clinic visit and assayed for inflammatory markers. Multilevel models estimated trait affective reactivity slopes for each participant, which were inputted into regression models to predict inflammation.

RESULTS

People who experienced greater decreases in positive affect on days when stressors occurred (i.e., positive affect reactivity) had elevated log IL-6, independent of demographic, physical, psychological, and behavioral factors (B = 1.12, SE = 0.45, p = .01). Heightened negative affect reactivity was associated with higher log CRP among women (p = .03) but not men (p = .57); health behaviors accounted for this association in women.

CONCLUSIONS

Adults who fail to maintain positive affect when faced with minor stressors in everyday life appear to have elevated levels of IL-6, a marker of inflammation. Women who experience increased negative affect when faced with minor stressors may be at particular risk of elevated inflammation. These findings add to growing evidence regarding the health implications of affective reactivity to daily stressors.

Sex differences in depressive and socioemotional responses to an inflammatory challenge: implications for sex differences in depression

Substantial evidence demonstrates that inflammatory processes may underlie depression for a subset of patients, including work showing that healthy subjects exposed to an inflammatory challenge show increases in depressed mood and feelings of social disconnection. However, despite the fact that depression is two times as likely to occur in females than males, the vast majority of this work has been carried out in males. Thus, the objective of this study was to determine whether females (vs males) would show greater increases in proinflammatory cytokines, depressed mood, and social disconnection in response to an inflammatory challenge. One hundred and fifteen healthy participants (69 female) completed this double-blind, placebo-controlled, randomized clinical trial in which participants were randomly assigned to receive either a single infusion of low-dose endotoxin (derived from Escherichia coli; 0.8 ng/kg of body weight) or placebo (same volume of 0.9% saline). Interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), depressed mood, and feelings of social disconnection were assessed hourly. Results showed that endotoxin (vs placebo) led to increases in proinflammatory cytokines (TNF-α, IL-6), depressed mood, and feelings of social disconnection. Females exposed to endotoxin showed greater increases in depressed mood and feelings of social disconnection. Furthermore, increases in TNF-α and IL-6 were correlated with increases in social disconnection for females but not for males. These sex differences in the relationships between inflammatory and socioemotional responses to an inflammatory challenge may be particularly important for understanding why females are two times as likely as males to develop depressive disorders.

Stress induces endotoxemia and low-grade inflammation by increasing barrier permeability

Chronic non-communicable diseases (NCDs) are the leading causes of work absence, disability, and mortality worldwide. Most of these diseases are associated with low-grade inflammation. Here, we hypothesize that stresses (defined as homeostatic disturbances) can induce low-grade inflammation by increasing the availability of water, sodium, and energy-rich substances to meet the increased metabolic demand induced by the stressor. One way of triggering low-grade inflammation is by increasing intestinal barrier permeability through activation of various components of the stress system. Although beneficial to meet the demands necessary during stress, increased intestinal barrier permeability also raises the possibility of the translocation of bacteria and their toxins across the intestinal lumen into the blood circulation. In combination with modern life-style factors, the increase in bacteria/bacterial toxin translocation arising from a more permeable intestinal wall causes a low-grade inflammatory state. We support this hypothesis with numerous studies finding associations with NCDs and markers of endotoxemia, suggesting that this process plays a pivotal and perhaps even a causal role in the development of low-grade inflammation and its related diseases.

Salivary cytokines as a minimally-invasive measure of immune functioning in young children: correlates of individual differences and sensitivity to laboratory stress

There is growing interest in minimally-invasive measures of environmentally-responsive biological systems in developmental science. Contributing to that endeavor, this study explores the intercorrelations, correlates, and task-sensitivity of proinflammatory salivary cytokines in childhood. Saliva was sampled from 125 healthy five-year old children (49% male) across a series of cognitive and emotional challenge laboratory tasks. Samples were assayed for cytokines (IL-1β, IL-6, IL-8, TNFα), and markers of hypothalamic-pituitary-adrenal (HPA) and autonomic nervous system (ANS) activation (salivary cortisol and alpha-amylase [sAA]). Cytokines were positively intercorrelated and task-sensitivity varied. Except IL-8, cytokines were elevated in children with oral health issues and tobacco smoke exposure. Among boys, cytokines were positively related to sAA and negatively related to cortisol. The findings suggest that in healthy children, salivary cytokine levels reflect compartmentalized oral immune activity. Associations between ANS and HPA activity and cytokines in saliva may present opportunities for minimally-invasive methods to explore neuroendocrine-immune interactions during development.

Greater amygdala activity and dorsomedial prefrontal-amygdala coupling are associated with enhanced inflammatory responses to stress

Psychological stress is implicated in the etiology of many common chronic diseases and mental health disorders. Recent research suggests that inflammation may be a key biological mediator linking stress and health. Nevertheless, the neurocognitive pathways underlying stress-related increases in inflammatory activity are largely unknown. The present study thus examined associations between neural and inflammatory responses to an acute laboratory-based social stressor. Healthy female participants (n=31) were exposed to a brief episode of stress while they underwent an fMRI scan. Blood samples were taken before and after the stressor, and plasma was assayed for markers of inflammatory activity. Exposure to the stressor was associated with significant increases in feelings of social evaluation and rejection, and with increases in levels of inflammation. Analyses linking the neural and inflammatory data revealed that heightened neural activity in the amygdala in response to the stressor was associated with greater increases in inflammation. Functional connectivity analyses indicated that individuals who showed stronger coupling between the amygdala and the dorsomedial prefrontal cortex (DMPFC) also showed a heightened inflammatory response to the stressor. Interestingly, activity in a different set of neural regions was related to increases in feelings of social rejection. These data show that greater amygdala activity in response to a stressor, as well as tighter coupling between the amygdala and the DMPFC, are associated with greater increases in inflammatory activity. Results from this study begin to identify neural mechanisms that might link stress with increased risk for inflammation-related disorders such as cardiovascular disease and depression.