Autonomic nervous system activity predicts increasing serum cytokines in children

The Interplay of Peer Victimization and Parasympathetic Nervous System Activity on Acute Inflammatory Stress Responses in Adolescence

This study examined the extent to which adolescent peer victimization predicted acute inflammatory responses to stress, and whether both resting parasympathetic nervous system (PNS) activity and PNS stress reactivity moderated this association. 83 adolescents (Mage = 14.89, SDage = 0.52, 48% female) reported their history of peer victimization and were exposed to a standardized social stress task before and after which dried blood spot samples were collected to assay inflammatory markers. Inflammatory responses to the stress task were assessed with a latent inflammatory change factor using the cytokines interleukin-6 (IL-6), interleukin-10 (IL-10), and tumor necrosis factor-α (TNF-α). PNS functioning, indexed by high-frequency heart rate variability, was measured at rest and during the stressor. Contrary to hypotheses, analyses revealed no direct relation between peer victimization and acute inflammatory responses, and resting PNS activity did not moderate this association. However, peer victimization predicted stronger inflammatory responses among adolescents with weaker PNS reactivity to the stress task (b = 0.63, p = .02). This association was not observed among adolescents with stronger PNS reactivity, for whom a negative but non-significant trend was found. Weaker PNS reactivity may thus indicate victimized adolescents' vulnerability for acute inflammatory responses, whereas stronger PNS reactivity may indicate adolescents' resilience to a social stressor.

Do dyadic interventions impact biomarkers of child health? A state-of-the-science narrative review

BACKGROUND

Early life adversity is related to numerous poor health outcomes in childhood; however, dyadic interventions that promote sensitive and responsive caregiving may protect children from the negative consequences of such exposures. To date, quasi-experimental and randomized controlled trials (RCTs) have examined the impact of dyadic interventions on a range of individual biomarkers in children, which may elucidate the relation between early stress exposure and transdiagnostic risk factors for prospective poor health. However, the content of interventions, analytic strategies, and findings vary widely across studies, obscuring key themes in the science and hindering policy and research efforts.

METHODS

We use a narrative approach to review findings from methodologically rigorous (predominantly RCT) studies of dyadic interventions' impacts on different biomarkers in children, including indicators of the hypothalamic-pituitary-adrenal (HPA) axis, parasympathetic (PNS) and sympathetic nervous systems (SNS), brain development, inflammation, and intracellular DNA processes. We contribute to this important area of inquiry through integrating findings across biological systems and identifying contextual and mechanistic factors to depict the current state of the field.

RESULTS

Evidence suggests dyadic interventions improved PNS functioning and advanced brain maturation. Some studies indicated interventions reduced hair cortisol concentrations, systemic inflammation, and resulted in differences in DNA methylation patterns. Findings did not support main effect-level change in salivary measures of HPA axis activity, SNS activity, or telomere length. Importantly, reviewed studies indicated significant heterogeneity in effects across biological systems, underscoring the importance of contextual factors (e.g., adversity subtype and severity) as potential moderators of effects. Further, findings suggested enhanced parenting behaviors may be a mechanism through which dyadic interventions operate on biomarkers.

CONCLUSIONS

We close with future policy and research directions, emphasizing the promise of biologically-informed dyadic interventions for understanding and ameliorating the effects of early adversity on transdiagnostic biomarkers of health.

The Vagal Nerve, Inflammation, and Diabetes-A Holy Triangle

Type 2 diabetic mellitus (T2DM) is a common chronic disease and a substantial risk factor of other fatal illnesses. At its core is insulin resistance, where chronic low-level inflammation is among its main causes. Thus, it is crucial to modulate this inflammation. This review paper provides scientific neuroimmunological evidence on the protective roles of the vagal nerve in T2DM. First, the vagus inhibits inflammation in a reflexive manner via neuroendocrine and neuroimmunological routes. This may also occur at the level of brain networks. Second, studies have shown that vagal activity, as indexed by heart-rate variability (HRV), is inversely related to diabetes and that low HRV is a predictor of T2DM. Finally, some emerging evidence shows that vagal nerve activation may reduce biomarkers and processes related to diabetes. Future randomized controlled trials are needed to test the effects of vagal nerve activation on T2DM and its underlying anti-inflammatory mechanisms.

Induction of tetraspanin 13 contributes to the synergistic anti-inflammatory effects of parasympathetic and sympathetic stimulation in macrophages

The autonomic nervous system plays an important role in the regulation of peripheral inflammation. Sympathetic nervous activation stimulates inflammatory gene expression and cytokines, whereas parasympathetic nervous activation suppresses the production of inflammatory cytokines by immune cells. However, most studies on the relationship between the autonomic nervous system and immune processes have analyzed a single branch of the autonomic nerves in isolation. Therefore, this study aimed to examine the effects of sympathetic and parasympathetic stimulation on macrophages, which are controlled by autonomic regulation. Macrophages were stimulated with lipopolysaccharide (LPS) to induce TNF-α. Then, the effects of β2 adrenergic receptor and α7 nicotinic acetylcholine receptor activation on TNF-α production were assessed using concentration-dependent assays. RNA-seq data were also used to identify genes whose expression was enhanced by parasympathetic and sympathetic stimulation. The simultaneous activation of β2 adrenergic receptors and α7 nicotinic acetylcholine receptors suppressed LPS-induced TNF-α production in a concentration-dependent manner. Moreover, simultaneous activation of these receptors had synergistic anti-inflammatory effects and induced Tspan13 expression, thereby contributing to anti-inflammatory mechanisms in macrophages. Our study revealed the synergistic anti-inflammatory effects of the parasympathetic and sympathetic stimulation of macrophages. Our results suggest that targeting both sympathetic and parasympathetic signaling is a promising therapeutic approach for inflammatory diseases.

Neuromodulation as a Potential Disease-Modifying Therapy for Osteoarthritis

PURPOSE OF REVIEW

The following review discusses the therapeutic potential of targeting the autonomic nervous system (ANS) for osteoarthritis (OA) treatment and encourages the field to consider the candidacy of bioelectronic medicine as a novel OA treatment strategy.

RECENT FINDINGS

The study of OA pathogenesis has focused on changes occurring at the joint level. As such, treatments for OA have been aimed at the local joint environment, intending to resolve local inflammation and decrease pain. However, OA pathogenesis has shown to be more than joint wear and tear. Specifically, OA-related peripheral and central sensitization can prompt neuroplastic changes in the nervous system beyond the articular joint. These neuroplastic changes may alter physiologic systems, like the neuroimmune axis. In this way, OA and related comorbidities may share roots in the form of altered neuroimmune communication and autonomic dysfunction. ANS modulation may be able to modify OA pathogenesis or reduce the impact of OA comorbidities. Moreover, blocking chronic nociceptive drive from the joint may help to prevent maladaptive nervous system plasticity in OA.

Impact of Non-Pharmacological Interventions on the Mechanisms of Atherosclerosis

Atherosclerosis remains the leading cause of mortality and morbidity worldwide characterized by the deposition of lipids and fibrous elements in the form of atheroma plaques in vascular areas which are hemodynamically overloaded. The global burden of atherosclerotic cardiovascular disease is steadily increasing and is considered the largest known non-infectious pandemic. The management of atherosclerotic cardiovascular disease is increasing the cost of health care worldwide, which is a concern for researchers and physicians and has caused them to strive to find effective long-term strategies to improve the efficiency of treatments by managing conventional risk factors. Primary prevention of atherosclerotic cardiovascular disease is the preferred method to reduce cardiovascular risk. Fasting, a Mediterranean diet, and caloric restriction can be considered useful clinical tools. The protective impact of physical exercise over the cardiovascular system has been studied in recent years with the intention of explaining the mechanisms involved; the increase in heat shock proteins, antioxidant enzymes and regulators of cardiac myocyte proliferation concentration seem to be the molecular and biochemical shifts that are involved. Developing new therapeutic strategies such as vagus nerve stimulation, either to prevent or slow the disease’s onset and progression, will surely have a profound effect on the lives of millions of people.

Associations of air pollution with peripheral inflammation and cardiac autonomic physiology in children

Climate change-related disasters have drawn increased attention to the impact of air pollution on health. 122 children ages 9-11 years old, M(SD) = 9.91(.56), participated. Levels of particulate matter (PM2.5) near participants' homes were obtained from the Environmental Protection Agency. Cytokines were assayed from 100 child serum samples: IL-6, IL-8, IL-10, and TNFα. Autonomic physiology was indexed by pre-ejection period (PEP), respiratory sinus arrhythmia (RSA), cardiac autonomic regulation (CAR), and cardiac autonomic balance (CAB). IL-6 was positively related to daily PM2.5 (r = .26, p = .009). IL-8 was negatively associated with monthly PM2.5 (r = -.23, p = .02). PEP was positively related to daily (r = .29, p = .001) and monthly PM2.5 (r = .18, p = .044). CAR was negatively associated with daily PM2.5 (r = -.29, p = .001). IL-10, TNFα, RSA, and CAB were not associated with PM2.5. Air pollution may increase risk of inflammation in children.

Respiratory Sinus Arrhythmia as a Physiological Resilience Marker for Children's Health

OBJECTIVE

The current study aimed to test parasympathetic nervous system activity, indexed through resting respiratory sinus arrhythmia (RSA) as a resilience factor that moderates the associations between socioeconomic status (SES), circulating cytokines, and somatic health in children.

METHODS

The sample included 181 parent-child dyads (mean [standard deviation] child age = 9.91 [0.57] years; 50.3% boys). Parents reported on family income, parental education, and subjective social status, to index SES. Children provided serum samples for assaying circulating inflammatory cytokines and had RSA measured during a 5-minute seated resting period. We used a composite measure of inflammation that combined standardized measures of interleukin 6, interleukin 10, and tumor necrosis factor α. Parents reported on their child's global health impairment and number of chronic health conditions.

RESULTS

Lower SES was associated with poorer global health, and higher levels of inflammation were associated with poorer global health, but these associations were not significant among children with high resting RSA. Specifically, resting RSA moderated the association between SES and global health impairment (B = 0.09, standard error [SE] = 0.02, p < .001). Preliminary evidence suggests that resting RSA may also moderate the association between inflammation and global health impairment (B = -0.12, SE = 0.03, p < .001), although this effect was no longer significant after Winsorizing an outlier value of a child with high global health impairment (B = -0.06, SE = 0.03, p = .04).

CONCLUSIONS

High resting RSA may represent a physiological profile of resilience in children, weakening the associations between low SES and poor somatic health, and between greater inflammation and poor somatic health.

The impact of social disadvantage on autonomic physiology of latinx adolescents: The role of environmental risks

The experience of poverty embodies complex, multidimensional stressors that may adversely affect physiological and psychological domains of functioning. Compounded by racial/ethnic discrimination, the financial aspect of family poverty typically coincides with additional social and physical environmental risks such as pollution exposure, housing burden, elevated neighborhood unemployment, and lower neighborhood education levels. In this study, we investigated the associations of multidimensional social disadvantage throughout adolescence with autonomic nervous system (ANS) functioning at 17 years. Two hundred and twenty nine low-income Mexican-American adolescents (48.6% female) and their parents were assessed annually between the ages of 10 and 16. Participants' census tracts were matched with corresponding annual administrative data of neighborhood housing burden, education, unemployment, drinking water quality, and fine particulate matter. We combined measures of adolescents' electrodermal response and respiratory sinuses arrhythmia at rest and during a social exclusion challenge (Cyberball) to use as ANS indices of sympathetic and parasympathetic activity, respectively. Controlling for family income-to-needs, youth exposed to greater cumulative water and air pollution from ages 10-16 displayed altered patterns of autonomic functioning at rest and during the social challenge. Conversely, youth living in areas with higher housing burden displayed healthy patterns of autonomic functioning. Altogether, results suggest that toxin exposure in youths' physical environments disrupts the ANS, representing a plausible mechanism by which pollutants and social disadvantage influence later physical and mental health.

Resting parasympathetic nervous system activity is associated with greater antiviral gene expression

Parasympathetic nervous system activity can downregulate inflammation, but it remains unclear how parasympathetic nervous system activity relates to antiviral activity. The present study examined associations between parasympathetic nervous system activity and cellular antiviral gene regulation in 90 adolescents (M_age = 16.28, SD = 0.73; 51.1% female) who provided blood samples and measures of cardiac respiratory sinus arrhythmia (RSA), twice, five weeks apart. Using a multilevel analytic framework, we found that higher RSA (an indicator of higher parasympathetic nervous system activity)-both at rest and during paced breathing-was associated with higher expression of Type I interferon (IFN) response genes in circulating leukocytes, even after adjusting for demographic and biological covariates. RSA was not associated with a parallel measure of inflammatory gene expression. These results identify a previously unrecognized immunoregulatory aspect of autonomic nervous system function and highlight a potential biological pathway by which parasympathetic nervous system activity may relate to health.

Heart Rate Variability and Circulating Inflammatory Markers in Midlife

Theoretical perspectives and empirical evidence suggest that the parasympathetic nervous system engages in active monitoring and moderating of inflammatory processes. A clearer understanding of the bidirectional communication between the parasympathetic nervous system and the immune system could lead to novel clinical interventions for inflammatory illnesses. The current study used a large (N ​= ​836) nationally representative sample of adults in the United States to investigate the associations between resting parasympathetic modulation of the heart, indexed through both high frequency heart rate variability (HF-HRV) and low frequency heart rate variability (LF-HRV), and six circulating markers of inflammation. Statistical analyses revealed robust inverse associations of HF-HRV with interleukin-6 (IL6), C-reactive protein (CRP), and fibrinogen, with or without covariate adjustment. Similar inverse associations were observed between LF-HRV and IL6 and CRP. No significant associations were observed between HRV and either inflammatory adhesion molecules (E-selectin, intracellular adhesion molecule-1) or soluble IL6 receptor. Results are consistent with the cholinergic anti-inflammatory pathway and suggest that parasympathetic modulation of inflammation through the vagus nerve may act on specific inflammatory molecules more than others.

A Close Examination of the Use of Systolic Time Intervals in the Calculation of Impedance Derived Cardiac Autonomic Balance and Regulation

Traditionally, impedance derived measures of cardiac autonomic balance (CAB) and regulation (CAR) are calculated using indices of heart rate variability (HRV) that primarily reflect parasympathetic nervous system activity (e.g., high-frequency HRV | HF-HRV) and pre-ejection period (PEP; a systolic time interval and measure of sympathetic activity). However, HF-HRV and PEP are considered measures of chronotropic and inotropic cardiac influence, respectively. Left ventricular ejection time (LVET) is a systolic time interval that reflects sympathetic chronotropic influence, and therefore may be a more appropriate measure for calculating CAB and CAR compared to PEP. Thus, the current study evaluates both PEP and LVET in the calculation of CAB and CAR. Data from 158 healthy participants (mean age = 19.09 years old, SD = 1.84 years) were available for analyses. CAB and CAR values were calculated using both HF-HRV and the root mean square of successive differences, in addition to both PEP and LVET, in accordance with previously established guidelines. Analyses showed that correlations were significantly weaker between CAB and CAR calculated using LVET for both HF (z = 5.12, p < 0.001) and RMSSD (z = 5.26, p < 0.001) than with PEP. These data suggest that LVET, compared to PEP, provides better “autonomic space” as evidenced by a lack of correlation between CAB and CAR computed using LVET. We stress that future research consider calculating CAB and CAR using chronotropic measures for both parasympathetic and sympathetic activity, as doing so may yield more accurate and independent measures of cardiac autonomic activity compared to a mixture of inotropic (i.e., PEP) and chronotropic (i.e., HF-HRV) measures.

Children's altruism following acute stress: The role of autonomic nervous system activity and social support

Altruistic behavior after stress exposure may have important health and psychological benefits, in addition to broader societal consequences. However, so far experimental research on altruism following acute stress has been limited to adult populations. The current study utilized an experimental design to investigate how altruistic donation behavior among children may be influenced by (a) exposure to an acute social stressor, the Trier Social Stress Test modified for use with children (TSST-M), (b) individual differences in stress physiology, and (c) social support from a parent. The sample consisted of 180 children (54.9% male, 45.1% female; mean age = 9.92 years, SD = 0.56 years) randomly assigned to one of three conditions involving the TSST-M: (a) prepare for the TSST-M alone, (b) prepare for the TSST-M with a parent, and (c) no-stress control group. Results revealed that children made larger donations post-stressor if they were alone before the acute stressor, if they had moderate cardiac autonomic balance, reflecting both parasympathetic and sympathetic influence, and if they were older. Children who prepared for the TSST-M with social support from a parent made comparable donations as children in the no-stress control group, in accord with stress buffering models. Increased altruism following acute stress among children suggests that a comprehensive understanding of the human stress response needs to incorporate "tend-and-befriend" behavior-the tendency for humans to show increased altruistic behavior during times of distress.