Sympathetic nervous system regulation of immunity

Improved Sympathetic Activity With Short-Term Effects of Yoga in Young Adults

The purpose of this study was to clarify the heart rate variability (HRV) transition after a single yoga program. Participants were 22 females who were healthy university students and had never practiced yoga before. They practiced yoga while recording their HRV. Heart rate (HR), high frequency (HF; 0.15-0.4 Hz) as parasympathetic and low frequency (LF; 0.04-0.15 Hz) components were extracted, and then the LF/HF ratio as sympathetic and normalized units of HF HFnu = HF/(LF + HF) as parasympathetic modulation in autonomic activity were calculated. HR and HRV indices after yoga were divided into four 5-minute periods (after 5, 10, 15, and 20 minutes) and compared before yoga. HR and LF/HF at all periods after yoga were significantly lower than before yoga (P < .01, all). HF after yoga was not significantly changed, but HFnu after 5, 10, and 15 minutes was significantly higher than before yoga (P < .01, <.01, and =.02, respectively). The short-term effects of yoga on HRV implied a decrease in sympathetic modulation and a relative increase in parasympathetic modulation. Therefore, yoga may be used as a fast-acting alternative therapy to significantly improve sympathetic activity.

Neuroimmune mechanisms in fear and panic pathophysiology

Panic disorder (PD) is unique among anxiety disorders in that the emotional symptoms (e.g., fear and anxiety) associated with panic are strongly linked to body sensations indicative of threats to physiological homeostasis. For example, panic attacks often present with feelings of suffocation that evoke hyperventilation, breathlessness, or air hunger. Due to the somatic underpinnings of PD, a major focus has been placed on interoceptive signaling and it is recognized that dysfunctional body-to-brain communication pathways promote the initiation and maintenance of PD symptomatology. While body-to-brain signaling can occur via several pathways, immune and humoral pathways play an important role in communicating bodily physiological state to the brain. Accumulating evidence suggests that neuroimmune mediators play a role in fear and panic-associated disorders, although this has not been systematically investigated. Currently, our understanding of the role of immune mechanisms in the etiology and maintenance of PD remains limited. In the current review, we attempt to summarize findings that support a role of immune dysregulation in PD symptomology. We compile evidence from human studies and panic-relevant rodent paradigms that indicate a role of systemic and brain immune signaling in the regulation of fear and panic-relevant behavior and physiology. Specifically, we discuss how immune signaling can contribute to maladaptive body-to-brain communication and conditioned fear that are relevant to spontaneous and conditioned symptoms of PD and identify putative avenues warranting future investigation.

Does sympathetic nervous system modulate tumor progression? A narrative review of the literature

Objective

The role of the sympathetic nervous system (SNS) in tumor development, progression and metastasis is studied for more than half a century and is attracting more attention during the last years. In this narrative review, we aim to a chronological and methodological presentation of the most interesting and pioneering studies on the subject.

Methods

The complexity of the autonomic nervous system’s interaction with the immune system, its direct and indirect effects on tumors and their surrounding tissues, plus the diversity and heterogeneity in the design and methodology of the studies, provide hard-to-interpret data and, at times, controversial findings. Studies are categorized into four main groups regarding the distribution of sympathetic nerve fibers inside the tumor, the effect of sympathectomy on cancer progression, the role of neurotransmitters on tumor growth and the impact of sympathetic adrenergic signaling on the anti-tumor immune response.

Results

Studies from all four categories converge to a common point. There is strong evidence that SNS function plays a role in the development and progression of tumors and subsequently the modification of SNS function, locally or diffusely, can affect the course of tumor growth.

Conclusion

The impact of SNS function on cancer behavior may be exerted in two ways, directly via the sympathetic nerve fibers or through widely distributed neurotransmitters. Modification of them, combined or not with treatments altering the immune function, could be the target for future therapeutic implications.

Presidential Address 2011: Autonomic modes of control and health

Understanding psychosomatic relations, and their implications for heath, is importantly dependent on our conceptual and measurement models. The historical view of reciprocal control of the autonomic branches is applicable in some contexts, but not others. Control of the autonomic branches can vary reciprocally, independently, and even coactively. Assessment of sympathovagal balance, based on a reciprocal model of regulation of the autonomic branches, may have applications in orthostatic contexts and in insulin resistance in diabetes. However, it does not adequately capture the pattern of autonomic control that is relevant for myocardial infarction (MI; in humans) and experimental cardiac arrest (in mice). A measure of sympathovagal balance (cardiac autonomic balance) was predictive and informative of the autonomic contributions to diabetes but was blind to autonomic contributions to cardiac arrest and its sequelae. However, a metric designed to capture the coactivity dimension of cardiac autonomic regulation (CAR) was predictive of MI and its sequelae. Both human and animal model studies revealed that low CAR (low sympathetic and especially low parasympathetic control) predicted the occurrence of MI and the neuroinflammatory consequences of cardiac arrest. These effects were importantly modulated by social support in both humans and animals, via an apparent oxytocinergic pathway that impacts parasympathetic cardiac control and CAR, and thus neuroinflammation. Results indicate the importance of a physiologically meaningful model of autonomic control in understanding health implications of the modes of autonomic control.

Blue light reduces organ injury from ischemia and reperfusion

Evidence suggests that light and circadian rhythms profoundly influence the physiologic capacity with which an organism responds to stress. However, the ramifications of light spectrum on the course of critical illness remain to be determined. Here, we show that acute exposure to bright blue spectrum light reduces organ injury by comparison with bright red spectrum or ambient white fluorescent light in two murine models of sterile insult: warm liver ischemia/reperfusion (I/R) and unilateral renal I/R. Exposure to bright blue light before I/R reduced hepatocellular injury and necrosis and reduced acute kidney injury and necrosis. In both models, blue light reduced neutrophil influx, as evidenced by reduced myeloperoxidase (MPO) within each organ, and reduced the release of high-mobility group box 1 (HMGB1), a neutrophil chemotactant and key mediator in the pathogenesis of I/R injury. The protective mechanism appeared to involve an optic pathway and was mediated, in part, by a sympathetic (β3 adrenergic) pathway that functioned independent of significant alterations in melatonin or corticosterone concentrations to regulate neutrophil recruitment. These data suggest that modifying the spectrum of light may offer therapeutic utility in sterile forms of cellular injury.

Social interaction modulates autonomic, inflammatory, and depressive-like responses to cardiac arrest and cardiopulmonary resuscitation

Psychological factors, including depression and social isolation, are important determinants of cardiovascular health. The current study uses a well-validated mouse model of cardiac arrest/cardiopulmonary resuscitation (CA/CPR) to examine the effect of social environment on several pathophysiological and behavioral responses to cerebral ischemia. Male experimental mice were either housed in pairs with an ovariectomized female or socially isolated for the duration of the experiment. Cardiac arrest increased the mRNA expression of the proinflammatory cytokines TNF-α, IL-1β, and IL-6, as well as the microglia marker MAC-1; expression of each of these factors, except IL-6, was further increased among socially isolated mice. Furthermore, socially isolated animals exposed to the CA/CPR procedure displayed significantly higher levels of neuronal cell death and microglia staining within the hippocampus at 7 d following surgery. Social isolation also exacerbated CA/CPR-induced depressive-like behavior and cardiac autonomic dysregulation. In the absence of ischemic damage, social environment had no significant effect on the expression of neuronal cell death, autonomic cardiac control, or behavior. Together, these data suggest that social factors influence the pathophysiological trajectory following cardiac arrest.

Photoperiod alters autonomic regulation of the heart

Outside of the tropics, environmental conditions fluctuate in a generally predictable manner across the year. Many small mammals have evolved mechanisms, such as seasonal breeding and annual adjustments in physiology, morphology, and behavior, that promote winter survival when food is scarce and thermoregulation is challenging. Photoperiod (day length) is a cue used by many seasonal breeders to predict seasonal changes in environmental conditions. One system that is uniquely situated to mediate photoperiod-induced alterations in physiology is the autonomic nervous system (ANS). The 2 branches of the ANS are key regulators of immune responses, thermoregulation, and energy balance, functions that undergo marked shifts in baseline and reactivity following acclimation to short day lengths. Although previous studies have investigated the effects of photoperiod on ANS endpoints, this study examined the direct effects of photoperiod on integrated ANS function. To test the hypothesis that short day lengths increase parasympathetic and sympathetic tones, we maintained adult male Siberian hamsters (Phodopus sungorus) to either long or short photoperiods and then analyzed electrocardiogram recordings. Short day lengths increased both parasympathetic tone, as measured by respiratory sinus arrhythmia, and sympathetic control of the heart, measured with autonomic blockade. Additionally, short day lengths enhanced the withdrawal of parasympathetic control and the increase of sympathetic tone in response to acute restraint stress. Finally, these effects were discovered to be independent of circulating androgens. These data indicate that the ANS of Siberian hamsters undergoes profound changes following prolonged exposure to short winter-like day lengths.

Relationship between sympathetic nervous activity and inflammatory response after subarachnoid hemorrhage in a perforating canine model

The objective of the present study was to evaluate the correlation between sympathetic nerve activation and inflammatory response in the acute stage of subarachnoid hemorrhage (SAH) in a canine perforating model. SAH was induced by perforation of the basilar artery with the use of a microcatheter via the femoral artery in 20 mongrel dogs. Hemodynamic parameters and intracranial pressure were recorded, and blood sample for C3a, C5b-9, IL-6, IL-8 and noradrenaline kinetic determination were measured at 0, 5, 15, 30, 60, 120, and 180 min after SAH. Noradrenaline (pg/mL) increased abruptly from 104+/-59 to 2010+/-918 at 5 min after SAH. C3a and C5b-9 reached peak values at 15 min and IL-6 and IL-8 reached peak values at 30 min after SAH, respectively. The peak values of C3a and C5b-9 correlated positively with the peak value of noradrenaline (r=0.743 and r=0.753, respectively). The peak values of IL-6 and IL-8 also correlated positively with the peak values of noradrenaline (r=0.603 and r=0.681, respectively).These results suggest that a pronounced activation of the sympathetic nervous system and the inflammatory response occurs in acute stage of SAH. Significant association between the rate of spillover of norepinephrine to plasma and the plasma levels of inflammatory markers indicates that the two processes, sympathetic activation and immune response are quantitatively linked in early stage after SAH. The exact mechanisms underlying this phenomenon deserved further investigations.

The burden of the systemic inflammatory response predicts vasospasm and outcome after subarachnoid hemorrhage

INTRODUCTION

Subarachnoid hemorrhage (SAH) can trigger immune activation sufficient to induce the systemic inflammatory response syndrome (SIRS). This may promote both extra-cerebral organ dysfunction and delayed cerebral ischemia, contributing to worse outcome. We ascertained the frequency and predictors of SIRS after spontaneous SAH, and determined whether degree of early systemic inflammation predicted the occurrence of vasospasm and clinical outcome.

METHODS

Retrospective analysis of prospectively collected data on 276 consecutive patients admitted to a neurosciences intensive care unit with acute, non-traumatic SAH between 2002 and 2005. A daily SIRS score was derived by summing the number of variables meeting standard criteria (HR >90, RR >20, Temperature >38 degrees C, or <36 degrees C, WBC count <4,000 or >12,000). SIRS was considered present if two or more criteria were met, while SIRS burden over the first four days was calculated by averaging daily scores. Regression modeling was used to determine the relationship among SIRS burden (after controlling for confounders including infection, surgery, and corticosteroid use), symptomatic vasospasm, and outcome, determined by hospital disposition.

RESULTS

SIRS was present in over half the patients on admission and developed in 85% within the first four days. Factors associated with SIRS included poor clinical grade, thick cisternal blood, larger aneurysm size, higher admission blood pressure, and surgery for aneurysm clipping. Higher SIRS burden was independently associated with death or discharge to nursing home (OR 2.20/point, 95% CI 1.27-3.81). All of those developing clinical vasospasm had evidence of SIRS, with greater SIRS burden predicting increased risk for delayed ischemic neurological deficits (OR 1.77/point, 95% CI 1.12-2.80).

CONCLUSIONS

Systemic inflammatory activation is common after SAH even in the absence of infection; it is more frequent in those with more severe hemorrhage and in those who undergo surgical clipping. Higher burden of SIRS in the initial four days independently predicts symptomatic vasospasm and is associated with worse outcome.

Chemical sympathectomy increases susceptibility to ocular herpes simplex virus type 1 infection

The cornea is one of the most highly innervated tissues in the mammalian host. We hypothesized changes to cornea innervation through chemical sympathectomy would significantly alter the host response to the neurotropic viral pathogen, herpes simplex virus type 1 (HSV-1) following ocular infection. Mice treated with 6-hydroxydopamine hydrobromide displayed reduced tyrosine hydroxylase-positive fibers residing in the cornea. Sympathectomized mice were also found to show a transient rise in virus recovered in infected tissues and succumbed to infection in greater numbers. Whereas there were no differences in infiltrating leukocyte populations including HSV-1-specific cytotoxic T lymphocytes in the infected tissue, an increase in substance P and a decrease in IFN-gamma levels in the trigeminal ganglion but not brain stem of sympathectomized mice were noted. Sympathectomized mice treated with the neurokinin-1 receptor antagonist L703,606 had delayed mortality implicating the involvement of substance P in HSV-1-mediated death.

Clonidine reduces hypersensitivity and alters the balance of pro- and anti-inflammatory leukocytes after local injection at the site of inflammatory neuritis

Perineural alpha2-adrenoceptor activation relieves hypersensitivity induced by peripheral nerve injury or sciatic inflammatory neuritis. This effect is associated with a reduction in pro-inflammatory cytokines, as well as a reduction in local leukocyte number and their capacity to produce pro-inflammatory cytokines. Curiously, clonidine's antinociceptive effect appears with a 2-3-day delay after injection. Previous observations have shown that alpha-adrenoceptor activation induces apoptosis in leukocytes, which would reduce leukocyte number. Additionally, macrophage scavenging of apoptotic cells results in a shift to an anti-inflammatory phenotype, with expression of transforming growth factor (TGF)-beta1. We therefore examined the effects of perineural clonidine 24 h and 3 days after its injection on apoptosis, TGF-beta1 expression and lymphocyte and macrophage phenotype in acute sciatic inflammatory neuritis. Perineural clonidine reduced ipsilateral neuritis-induced hypersensitivity in a delayed manner (3 days after treatment), along with a reduction at this time in lymphocyte number and an increase in caspase-3 and TGF-beta1 expressing cells and macrophages co-expressing TGF-beta1 in the sciatic nerve. One day after injection clonidine treatment was associated with a reduction in lymphocytes and pro-inflammatory Th-1 cells as well as increased numbers of caspase-3 and TGF-beta1 expressing cells and macrophages co-expressing TGF-beta1 in sciatic nerve. Clonidine's effects were prevented by co-administration of an alpha2-adrenoceptor antagonist. These data suggest that alpha2-adrenoceptor activation in sciatic inflammatory neuritis increases local apoptosis and anti-inflammatory products early after treatment. This early effect likely underlies the delayed anti-inflammatory and anti-hypersensitivity effects of perineural clonidine in this setting.

Sympathetic activation and inflammatory response in patients with subarachnoid haemorrhage

OBJECTIVE

The aim of this study was to evaluate the correlation between sympathetic nervous activation and the immune response in patients following subarachnoid haemorrhage (SAH).

DESIGN AND SETTING

Clinical study in a neurosurgical intensive care unit.

PATIENTS AND PARTICIPANTS

Fourteen patients with acute non-traumatic SAH were included. Fifteen healthy, age-matched volunteers served as controls for measurement of catecholamine spillover.

INTERVENTION

Blood sampling for C3a, C5b-9, IL-6, IL-8 and norepinephrine kinetic determination was made within 48 h, at 72 h and on the 7th-10th day after the SAH.

MEASUREMENTS AND RESULTS

SAH patients exhibited a profound increase in the rate of norepinephrine spillover to plasma at 48 h, 72 h and 7-10 days after the insult, 3-4 times that in healthy individuals. The plasma levels of C3a, IL-6 and C5b-9 were significantly elevated at 48 h, at 72 h and 7-10 days after the SAH, but the plasma level of IL-6 decreased significantly 7-10 days after the SAH. There was no relationship between the magnitude of sympathetic activation and the levels of inflammatory markers.

CONCLUSIONS

Following SAH a pronounced activation of the sympathetic nervous system and the inflammatory system occurs. The lack of significant association between the rate of spillover of norepinephrine to plasma and the plasma levels of inflammatory markers indicates that the two processes, sympathetic activation and the immune response, following SAH are not quantitatively linked. In spite of a persistent high level of sympathetic activation the plasma level of IL-6 decreased significantly one week after SAH.

Norman Cousins Lecture. The uses and abuses of psychoneuroimmunology: a global overview

Studies of interactions between the nervous and immune systems that effect immunological and behavioral changes are relevant to our understanding biological issues pertinent to evolution, ethology, ecology, and aging, in addition to our understanding the immune and nervous systems per se. Psychoneuroimmunology also relates to homeland security, science education, and the practice of conventional as well as complementary and alternative medicine. This paper will highlight just some of these global implications of psychoneuroimmunology.

Alpha2-adrenoceptor stimulation transforms immune responses in neuritis and blocks neuritis-induced pain

Neuropathic pain may be primarily driven by immune responses in peripheral nerves. Peripherally released catecholamines may exacerbate neuropathic pain and also modulate immune responses in a complex and sometimes opposing manner by actions on multiple adrenoceptor subtypes. We showed previously that injection of the alpha2-adrenoceptor agonist clonidine at the site of peripheral nerve injury reduces pain behavior and local tissue pro-inflammatory cytokine content in rats. The current study used a model of acute inflammatory neuritis to test the efficacy and mechanisms of action of alpha2-adrenoceptor stimulation to reduce pain. Zymosan, injected on the sciatic nerve, caused hypersensitivity to mechanical stimuli ipsilateral to injection and contralaterally, so-called mirror image pain. Ipsilateral hypersensitivity was inhibited dose-dependently by perineural injection of clonidine. Zymosan increased leukocyte number at the site of injection 3 d later as well as their content of interleukin 1alpha (IL-1alpha), IL-1beta, and IL-6. Perineural clonidine prevented both the increase in leukocyte number and cytokine expression induced by zymosan. Additionally, clonidine reduced the capacity of leukocytes to express pro-inflammatory cytokines as assessed by treatment of cells ex vivo with lipopolysaccharide, whereas no repression of IL-10 production occurred. Clonidine reduced the number of macrophages and lymphocytes as well as their expression of tumor necrosis factor alpha. All of the effects of clonidine were prevented by coadministration of an alpha2A-adrenoceptor-preferring antagonist. These results suggest that alpha2-adrenoceptor stimulation transforms cytokine gene expression, especially in macrophages and lymphocytes from a pro- to an anti-inflammatory profile in the setting of neuritis, likely relieving neuritis-induced pain by this mechanism.

Norepinephrine, dopamine and dexamethasone modulate discrete leukocyte subpopulations and cytokine profiles from human PBMC

The interplay between the immune and neuroendocrine systems is intense, with the cross-talk between these two systems increasing during stress circumstances. Stress events culminate with hormonal pathway activation elevating the plasma levels of glucocorticoids and catecholamines. The majority of the works evaluating the effects of stress hormones on immune cells have utilized in vivo animal models or clinical studies. This work evaluates the effects of norepinephrine, dopamine, dexamethasone, and the combination of norepinephrine and dexamethasone on cellular activation and expression of immunoregulatory cytokines and chemokines by human PBMC in vitro. Norepinephrine and dopamine increased lymphocyte activation accompanied by augmented Th1 and Th2 type cytokine production. Dexamethasone reduced cell activation and decreased frequencies of cytokine producing cells and chemokine production. The action of norepinephrine together with dexamethasone resulted in immunosupression. The observed effects of hormones and neurotransmitters on leukocyte subsets likely underlie their immunomodulatory action in vivo.

Aging and sympathetic modulation of immune function in Fischer 344 rats: effects of chemical sympathectomy on primary antibody response

In aged Fischer 344 (F334) rats, sympathetic innervation of the spleen is markedly diminished compared with young rats. To determine if this diminished noradrenergic (NA) innervation maintains a functional connection with the immune system, 3- and 17-month-old male F344 rats were treated with the NA-selective neurotoxin, 6-hydroxydopamine (6-OHDA), to ablate peripheral NA nerve fibers. In sympathectomized rats immunized with keyhole limpet hemocyanin (KLH), a T-dependent protein antigen, anti-KLH IgM, IgG, IgG1, IgG2b antibody titers were increased in young and old rats 14 days after immunization compared to vehicle controls. Furthermore, the number of IgM and IgG anti-KLH antibody-secreting spleen cells was elevated 7 and 14 days post-immunization. These effects were prevented by pretreatment with desipramine, a catecholamine uptake blocker that blocks 6-OHDA uptake and subsequent sympathectomy. Chemical sympathectomy also increased KLH-induced proliferation in vitro by spleen cells from old, but not young animals. Isoproterenol (ISO), a beta-adrenergic receptor agonist, elicited a rise in cAMP in spleen cells from NA-intact young and old rats, but the increase was attenuated in spleen cells from old rats. These results demonstrate that, although NA innervation in the F344 rat spleen is diminished with age, sympathetic signaling of the immune system remains intact. Thus, the SNS can inhibit antibody produced in response to a protein antigen in both young and old F344 rats.

Brain-immune interactions and disease susceptibility

Many studies have established the routes by which the immune and central nervous (CNS) systems communicate. This network of connections permits the CNS to regulate the immune system through both neuroendocrine and neuronal pathways. In turn, the immune system signals the CNS through neuronal and humoral routes, via immune mediators and cytokines. This regulatory system between the immune system and CNS plays an important role in susceptibility and resistance to autoimmune, inflammatory, infectious and allergic diseases. This review focuses on the regulation of the immune system via the neuroendocrine system, and underlines the link between neuroendocrine dysregulation and development of major depressive disorders, autoimmune diseases and osteoporosis.