Stress-induced immune suppression: role of brain corticotropin releasing hormone and autonomic nervous system mechanisms

Association between intraoperative dexmedetomidine and all-cause mortality and recurrence after laparoscopic resection of colorectal cancer: Follow-up analysis of a previous randomized controlled trial

Background

Dexmedetomidine (DEX) has been widely applied in the anesthesia and sedation of patients with oncological diseases. However, the potential effect of DEX on tumor metastasis remains contradictory. This study follows up on patients who received intraoperative DEX during laparoscopic resection of colorectal cancer as part of a previous clinical trial, examining their outcomes 5 years later.

Methods

Between June 2015 and December 2015, 60 patients undergoing laparoscopic colorectal resection were randomly assigned to the DEX and control groups. The DEX group received an initial loading dose of 1μ/kg before surgery, followed by a continuous infusion of 0.3μg/kg/h during the operation and the Control group received an equivalent volume of saline. A 5-year follow-up analysis was conducted to evaluate the overall survival, disease-free survival, and tumor recurrence.

Results

The follow-up analysis included 55 of the 60 patients. The DEX group included 28 patients, while the control group included 27 patients. Baseline characteristics were comparable between the two groups, except for vascular and/or neural invasion of the tumor in the DEX group (9/28 vs. 0/27, p = 0.002). We did not observe a statistically significant benefit but rather a trend toward an increase in overall survival and disease-free survival in the DEX group, 1-year overall survival (96.4% vs. 88.9%, p = 0.282), 2-year overall survival (89.3% vs. 74.1%, p = 0.144), 3-year overall survival (89.3% vs. 70.4%, p = 0.08), and 5-year overall survival (78.6% vs. 59.3%, p = 0.121). The total rates of mortality and recurrence between the two groups were comparable (8/28 vs. 11/27, p = 0.343).

Conclusion

Administration of DEX during laparoscopic resection of colorectal cancer had a nonsignificant trend toward improved overall survival and disease-free survival.

Clinical Trial Registration

http://www.chictr.org.cn/, identifier ChiCTRIOR-15006518.

The Role of Dexmedetomidine in Tumor-Progressive Factors in the Perioperative Period and Cancer Recurrence: A Narrative Review

Dexmedetomidine, a specific α2 adrenergic receptor agonist, is highly frequently used in the perioperatively for its favorable pharmacology, such as mitigating postoperative cognitive dysfunction. Increasing attention has been recently focused on the effect of whether dexmedetomidine influences cancer recurrence, which urges the discussion of the role of dexmedetomidine in tumor-progressive factors. The pharmacologic characteristics of dexmedetomidine, the tumor-progressive factors in the perioperative period, and the relationships between dexmedetomidine and tumor-progressive factors were described in this review. Available evidence suggests that dexmedetomidine could reduce the degree of immune function suppression, such as keeping the number of CD3+ cells, NK cells, CD4+/CD8+ ratio, and Th1/Th2 ratio stable and decreasing the level of proinflammatory cytokine (interleukin 6 and tumor necrosis factor-alpha) during cancer operations. However, dexmedetomidine exhibits different roles in cell biological behavior depending on cancer cell types. The conclusions on whether dexmedetomidine would influence cancer recurrence could not be currently drawn for the lack of strong clinical evidence. Therefore, this is still a new area that needs further exploration.

The Interplay between Autonomic Nervous System and Inflammation across Systemic Autoimmune Diseases

The autonomic nervous system (ANS) and the immune system are deeply interrelated. The ANS regulates both innate and adaptive immunity through the sympathetic and parasympathetic branches, and an imbalance in this system can determine an altered inflammatory response as typically observed in chronic conditions such as systemic autoimmune diseases. Rheumatoid arthritis, systemic lupus erythematosus, and systemic sclerosis all show a dysfunction of the ANS that is mutually related to the increase in inflammation and cardiovascular risk. Moreover, an interaction between ANS and the gut microbiota has direct effects on inflammation homeostasis. Recently vagal stimulation techniques have emerged as an unprecedented possibility to reduce ANS dysfunction, especially in chronic diseases characterized by pain and a decreased quality of life as well as in chronic inflammation.

Glucocorticoids and Catecholamines Affect in Vitro Functionality of Porcine Blood Immune Cells

Simple Summary

In modern livestock husbandry, animals may face stressful events like weaning, regrouping, or transportation, all of which can impair animal welfare and health. Research in model organisms has revealed that stress hormones, such as glucocorticoids and catecholamines, strongly modulate the immune system and thus the animals’ ability to fight infections. In the pig, knowledge about this relationship is rare, and results from rodents cannot readily be transferred due to some physiological differences. Therefore, the effects of glucocorticoids and catecholamines on porcine immune cell proliferation and the production of the pro-inflammatory cytokine TNFα were investigated in an in vitro study. Blood was obtained from catheterized pigs to exclude pre-exposure to stress hormones. Glucocorticoids exerted inhibitory effects on both investigated immune functions. Catecholamines, on the other hand, showed diverse effects on lymphocyte proliferation and TNFα production of particular immune cell types. This suggests that studies from model species are not entirely transferrable to pigs. Future research should extend the preliminary findings on cytokine production and focus on the molecular mechanisms and health impacts of stress hormones in pigs.

Abstract

Stress hormones exert important modulating influences on the functionality of immune cells. Despite its major role as a livestock animal and its increasing use as an animal model, knowledge about this relationship in the domestic pig is rare. This study therefore aimed to characterize the effect of glucocorticoids and catecholamines on the proliferation and cytokine production of porcine peripheral blood mononuclear cells (PBMC). Blood was obtained from donor pigs equipped with indwelling catheters to exclude stress hormone exposition before in vitro testing. PBMC were stimulated in the presence of cortisol, adrenaline or noradrenaline at concentrations resembling low to high stress conditions. Proliferation was determined via ³H-thymidine incorporation, and TNFα producers were quantified by intracellular cytokine staining. Cortisol led to a decrease in mitogen-induced lymphocyte proliferation and the number of TNFα producing cells. In contrast, catecholamines increased proliferation while exerting repressive or no effects on the number of cytokine producers. Remarkably, in concentrations presumably found in lymphatic tissue in stress situations, noradrenaline suppressed lymphocyte proliferation completely. The shown repressive effects might especially have implications on health and welfare in pigs. The obtained results provide a preliminary database for extended studies on the molecular mechanisms of glucocorticoid and catecholamine actions on porcine immune cells.

Stress Determined through Heart Rate Variability Predicts Immune Function

BACKGROUND

Stress is a prevalent health problem in modern society. If experienced for long periods of time it can lead to immune dysfunctions. Thus, public health management practices must include the assessment of stress. In health management settings, electrocardiography (ECG) is routinely used to assess cardiovascular health and make inferences about stress using information from heart rate variability (HRV). However, it is unclear whether stress assessment based on HRV can also be used to index immune function.

OBJECTIVES

To compare stress that was determined by a measure of HRV (pNN50) from ECG with immune function indices (neutrophil, monocyte, and lymphocyte percentages) obtained from blood samples.

METHODS

A total of 184 healthy adults participated in the study, which took place in an examination room at the Health Management Center of The Affiliated Hospital of Hangzhou Normal University, China. Participants viewed a relaxing video while having a 2-min ECG recorded. They were then taken to have their blood drawn as part of their physical examination. Measures of stress (pNN50) were extracted from ECG, while measures of immune function (percentages of neutrophils, monocytes, and lymphocytes) were extracted from blood samples.

RESULTS

Stress correlated positively with neutrophil percentages (r = 0.21) and negatively with monocyte (r = -0.16) and lymphocyte percentages (r = -0.18).

CONCLUSIONS

These findings show HRV analysis to be a potentially viable noninvasive and inexpensive method not only for indexing stress, but also predicting immune function, thus managing the health risks associated with stress.

Resilience and immunity

Resilience is the process that allows individuals to adapt to adverse conditions and recover from them. This process is favored by individual qualities that have been amply studied in the field of stress such as personal control, positive affect, optimism, and social support. Biopsychosocial studies on the individual qualities that promote resilience show that these factors help protect against the deleterious influences of stressors on physiology in general and immunity in particular. The reverse is also true as there is evidence that immune processes influence resilience. Most of the data supporting this relationship comes from animal studies on individual differences in the ability to resist situations of chronic stress. These data build on the knowledge that has accumulated on the influence of immune factors on brain and behavior in both animal and human studies. In general, resilient individuals have a different immunophenotype from that of stress susceptible individuals. It is possible to render susceptible individuals resilient and vice versa by changing their inflammatory phenotype. The adaptive immune phenotype also influences the ability to recover from inflammation-induced symptoms. The modulation of these bidirectional relationships between resilience and immunity by the gut microbiota opens the possibility to influence them by probiotics and prebiotics. However, more focused studies on the reciprocal relationship between resilience and immunity will be necessary before this can be put into practice.

Psychological Distress and Zika, Dengue and Chikungunya Symptoms Following the 2016 Earthquake in Bahía de Caráquez, Ecuador

On 16 April 2016, a 7.8 magnitude earthquake struck coastal Ecuador, resulting in significant mortality and morbidity, damages to infrastructure, and psychological trauma. This event coincided with the first outbreak of Zika virus (ZIKV) and co-circulation with dengue virus (DENV) and chikungunya virus (CHIKV). We tested whether the degree of psychological distress was associated with the presence of suspected DENV, CHIKV, ZIKV (DCZ) infections three months after the earthquake. In July 2016, 601 household members from four communities in Bahía de Caráquez, Manabí Province, Ecuador, were surveyed in a post-disaster health evaluation. Information was collected on demographics, physical damages and injuries, chronic diseases, self-reported psychological distress, and DCZ symptoms. We calculated the prevalence of arbovirus and distress symptoms by community. ANOVA was used to compare the mean number of psychological distress symptoms between people with versus without suspected DCZ infections by age, gender, community and the need to sleep outside of the home due to damages. The prevalence of suspected DCZ infections was 9.7% and the prevalence of psychological distress was 58.1%. The average number of psychological distress symptoms was significantly higher among people with suspected DCZ infections in the periurban community of Bella Vista, in women, in adults 40-64 years of age and in individuals not sleeping at home (p < 0.05). The results of this study highlight the need to investigate the interactions between psychological distress and arboviral infections following natural disasters.

Social instability and immunity in rhesus monkeys: the role of the sympathetic nervous system

Social instability can adversely affect endocrine, immune and health outcomes, and recent evidence suggests that the sympathetic nervous system (SNS) might mediate these effects. We conducted two studies with adult male rhesus monkeys (Macaca mulatta) to understand how social conditions affect measures of SNS activity and immune function. In Experiment 1, animals were socialized in stable social conditions, then were switched to unstable (stressful) social conditions, then were returned to stable conditions. Analysis revealed quadratic effects for measures of behaviour, urinary metabolites of epinephrine and norepinephrine, and expression of immune response genes: as expected, social instability adversely impacted most measures, and the effects remediated upon re-imposition of stable conditions. Cortisol levels were unaffected. In Experiment 2, we used the sympathomimetic drug methamphetamine to challenge the SNS; animals also underwent socialization in stable or unstable groups. Surprisingly, while methamphetamine elevated plasma catecholamines, responses in lymph nodes tracked the social, and not the drug, condition: social instability upregulated the density of SNS fibres in lymph nodes and downregulated Type I interferon gene expression. Together, these results indicate that the SNS is extremely sensitive to social conditions; full understanding of the adverse effects of social instability on health should therefore incorporate measures of this health-relevant system.

Sympathoadrenergic modulation of hematopoiesis: a review of available evidence and of therapeutic perspectives

Innervation of the bone marrow (BM) has been described more than one century ago, however the first in vivo evidence that sympathoadrenergic fibers have a role in hematopoiesis dates back to less than 25 years ago. Evidence has since increased showing that adrenergic nerves in the BM release noradrenaline and possibly also dopamine, which act on adrenoceptors and dopaminergic receptors (DR) expressed on hematopoietic cells and affect cell survival, proliferation, migration and engraftment ability. Remarkably, dysregulation of adrenergic fibers to the BM is associated with hematopoietic disturbances and myeloproliferative disease. Several adrenergic and dopaminergic agents are already in clinical use for non-hematological indications and with a usually favorable risk-benefit profile, and are therefore potential candidates for non-conventional modulation of hematopoiesis.

Reproductive and immune effects of chronic corticosterone treatment in male White's treefrogs, Litoria caerulea

Amphibian populations are declining globally. The potential contribution of glucocorticoid hormones to these declines has received little attention, but chronic elevation of glucocorticoids has been linked to a suite of negative outcomes across vertebrate taxa. Recently, chronic environmental stress has been associated with precipitous declines in sperm count and sperm viability in White's treefrogs (Litoria caerulea), but the mechanism remains unknown. In order to determine whether corticosterone is responsible for suppressing reproductive and immune function in this species, we elevated circulating concentrations of corticosterone in 10 male captive-bred frogs via transdermal application for 7 days. We compared sperm count, sperm viability, splenic cell count and circulating leucocyte counts in corticosterone-treated frogs with those in untreated control frogs. Chronic application of exogenous corticosterone led to supraphysiological circulating concentrations of corticosterone, but had no effect on sperm count or viability. However, corticosterone-treated frogs demonstrated a significant decrease in circulating eosinophils, which are immune cells implicated in fighting a variety of pathogens, including extracellular parasites. These findings suggest that although chronic elevation of circulating corticosterone is not necessarily associated with reproductive suppression in this species, it may cause immunosuppression. Thus, chronic glucocorticoid elevations in amphibians might enhance susceptibility to infection with pathogens and parasites, and their potential contributions to global population declines warrant further study.

Increased depression, diabetes and diabetic complications in Graves' disease patients in Asia

BACKGROUND

This study aimed to evaluate the risk of depression and other cardiovascular comorbidities in Graves' disease (GD) patients in Asia.

METHODS

The study patients were all newly diagnosed with GD [International Classification of Disease, 9th Revision, Clinical Modification (ICD-9-CM) 242.0] from January 1998 to December 2008. Patients aged <20 years or those with preexisting mental disorder (ICD-9-CM 290-319) were excluded from analyses. Control patients were randomly selected for the non-GD cohort, 1:4 frequency matched to the GD cohort according to sex, age and index year. The same exclusion criteria applied to the GD cohort were applied to the non-GD cohort. The GD cohort contained 4195 patients and the non-GD cohort contained 16 780 patients.

RESULTS

The GD patients were more likely to have diabetes (8.03% vs. 4.48%, P < 0.0001), hypertension (18.1% vs. 13.5%, P < 0.0001), hyperlipidemia (11.9% vs. 9.09%, P < 0.0001) and coronary artery disease (10.3% vs. 5.86%, P < 0.0001) than the control patients were. The GD patients were also associated with significantly higher risk of depression than the control patients were (hazard ratio = 1.69, 95% confidence interval = 1.45-1.96).

CONCLUSION

GD and GD treatment are associated with increased risk of depression diabetes and diabetic complications in Asian patients.

Effects of dexmedetomidine on the ratio of T helper 1 to T helper 2 cytokines in patients undergoing laparoscopic cholecystectomy

STUDY OBJECTIVES

To investigate the effect of dexmedetomidine on T helper 1 (Th1) and T helper 2 (Th2) cytokines and their ratio during and after surgery.

DESIGN

Single-blinded, randomized, placebo-controlled clinical comparison study.

SETTING

Academic medical center.

PATIENTS

46 adult, ASA physical status 1 and 2 patients scheduled for laparoscopic cholecystectomy.

INTERVENTIONS

Patients were randomized to two groups: the dexmedetomidine group (n = 23), in which dexmedetomidine was infused with a 1.0 μg/kg loading dose followed by infusion of 0.5 μg/kg/h; or the saline group (n = 23).

MEASUREMENTS

Interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) as Th1 and Th2 cytokines, respectively, were quantified three times: after induction of anesthesia (T0), at the end of peritoneal closure (T1), and 60 minutes after surgery (T2). The IFN-gamma/IL-4 ratio was then calculated.

MAIN RESULTS

The dexmedetomidine group displayed higher levels of IFN-gamma at T1 and T2 (42.30 pg/dL vs 6.91 pg/dL at T1 [P = 0.025]; 40.51 pg/dL vs 8.29 pg/dL at T2 [P = 0.030]) than the saline group. The dexmedetomidine group was also associated with higher ratios of IFN-gamma/IL-4 (1.22 vs 0.32, respectively, at T1 [P = 0.012]; 1.53 vs 0.13, respectively, at T2 [P = 0.012]).

CONCLUSIONS

Dexmedetomidine plays an immunomodulatory role, shifting the Th1/Th2 cytokine balance toward Th1 in patients with surgical and anesthetic stress.

Autonomic regulation of cellular immune function

The nervous system and the immune system (IS) are two integrative systems that work together to detect threats and provide host defense, and to maintain/restore homeostasis. Cross-talk between the nervous system and the IS is vital for health and well-being. One of the major neural pathways responsible for regulating host defense against injury and foreign antigens and pathogens is the sympathetic nervous system (SNS). Stimulation of adrenergic receptors (ARs) on immune cells regulates immune cell development, survival, proliferative capacity, circulation, trafficking for immune surveillance and recruitment, and directs the cell surface expression of molecules and cytokine production important for cell-to-cell interactions necessary for a coordinated immune response. Finally, AR stimulation of effector immune cells regulates the activational state of immune cells and modulates their functional capacity. This review focuses on our current understanding of the role of the SNS in regulating host defense and immune homeostasis. SNS regulation of IS functioning is a critical link to the development and exacerbation of chronic immune-mediated diseases. However, there are many mechanisms that need to be further unraveled in order to develop sound treatment strategies that act on neural-immune interaction to resolve or prevent chronic inflammatory diseases, and to improve health and quality of life.

Psychological stress and immunoprotection versus immunopathology in the skin

Stress is thought to suppress immune function and increase susceptibility to infections and cancer. Paradoxically, stress is also known to exacerbate autoimmune/proinflammatory disorders (eg, psoriasis, atopic dermatitis) that should be ameliorated by immunosuppression. Here we review studies showing that although chronic stress (lasting for weeks/months/years) can suppress/dysregulate immune function, acute stress (lasting for minutes to hours) can have immunoenhancing effects. Short-term stress experienced at the time of immune activation enhances dendritic cell, neutrophil, macrophage, and lymphocyte trafficking, maturation, and function, and has been shown to augment innate and adaptive immunity; therefore, depending on the conditions of immune activation, and the nature of the activating antigen, short-term stress can enhance the acquisition and expression of immunoprotection or immunopathology. In contrast, chronic stress suppresses or dysregulates innate and adaptive immune responses by altering the Type 1-Type 2 cytokine balance, inducing low-grade chronic increases in proinflammatory factors, and suppressing numbers, trafficking, and function of immunoprotective cells. Chronic stress also increases susceptibility to skin cancer by suppressing Type 1 cytokines and protective T cells while increasing regulatory/suppressor T cell number/function. It is important to recognize that the adaptive function of a physiological stress response is to promote survival. Stress-related neurotransmitters, hormones, and factors act as biological alarm signals that prepare the immune and other physiological systems for potential challenges (eg, wounding or infection) perceived by the brain (eg, detection of an attacker); however, this may exacerbate immunopathology (eg, psoriasis, atopic dermatitis) if the enhanced immune response is directed against innocuous or self-antigens, or if the system is chronically activated as seen during long-term stress. In view of the ubiquitous nature of stress and its significant effects on immunoprotection and immunopathology, it is important to further elucidate the mechanisms mediating both the salubrious and the harmful effects of stress, and to meaningfully translate findings from bench to bedside.

Interpreting Stress Responses during Routine Toxicity Studies

Stress often occurs during toxicity studies. The perception of sensory stimuli as stressful primarily results in catecholamine release and activation of the hypothalamic–pituitary–adrenal (HPA) axis to increase serum glucocorticoid concentrations. Downstream effects of these neuroendocrine signals may include decreased total body weights or body weight gain; food consumption and activity; altered organ weights (e.g., thymus, spleen, adrenal); lymphocyte depletion in thymus and spleen; altered circulating leukocyte counts (e.g., increased neutrophils with decreased lymphocytes and eosinophils); and altered reproductive functions. Typically, only some of these findings occur in a given study. Stress responses should be interpreted as secondary (indirect) rather than primary (direct) test article–related findings. Determining whether effects are the result of stress requires a weight-of-evidence approach. The evaluation and interpretation of routinely collected data (standard in-life, clinical pathology, and anatomic pathology endpoints) are appropriate and generally sufficient to assess whether or not changes are secondary to stress. The impact of possible stress-induced effects on data interpretation can partially be mitigated by toxicity study designs that use appropriate control groups (e.g., cohorts treated with vehicle and subjected to the same procedures as those dosed with test article), housing that minimizes isolation and offers environmental enrichment, and experimental procedures that minimize stress and sampling and analytical bias.

This article is a comprehensive overview of the biological aspects of the stress response, beginning with a Summary (Section 1) and an Introduction (Section 2) that describes the historical and conventional methods used to characterize acute and chronic stress responses. These sections are followed by reviews of the primary systems and parameters that regulate and/or are influenced by stress, with an emphasis on parameters evaluated in toxicity studies: In-life Procedures (Section 3), Nervous System (Section 4), Endocrine System (Section 5), Reproductive System (Section 6), Clinical Pathology (Section 7), and Immune System (Section 8). The paper concludes (Section 9) with a brief discussion on Minimizing Stress-Related Effects (9.1.), and a final section explaining why Parameters routinely measured are appropriate for assessing the role of stress in toxicology studies (9.2.).

Adrenergic modulation of immune cells: an update

Sympathoadrenergic pathways are crucial to the communication between the nervous system and the immune system. The present review addresses emerging issues in the adrenergic modulation of immune cells, including: the specific pattern of adrenoceptor expression on immune cells and their role and changes upon cell differentiation and activation; the production and utilization of noradrenaline and adrenaline by immune cells themselves; the dysregulation of adrenergic immune mechanisms in disease and their potential as novel therapeutic targets. A wide array of sympathoadrenergic therapeutics is currently used for non-immune indications, and could represent an attractive source of non-conventional immunomodulating agents.

Mood, Th-1/Th-2 cytokine profile, and autonomic activity in older adults with acute/decompensated heart failure: preliminary observations

In order to assess the relationships among mood, peripheral autonomic output and circulating immunoinflammatory mediators in older individuals with decompensated heart failure (CHF), 20 consecutive patients (78+/-7 years, 35% women) admitted to the coronary care unit with a clinical diagnosis of acute/decompensated CHF of coronary origin were examined. Mood was evaluated by the 21-item Hamilton Depression Scale (HAM-D). Four patients met the criteria for major depression. Heart rate variability (HRV) analysis and the levels of tumour necrosis factor (TNF)-alpha, interferon (IFN)-gamma, interleukin (IL)-2, IL-4, IL-6 and IL-10 were measured within 24-72 h of admission. A significant positive relationship between score in HAM-D and serum IL-6 levels was detected with a similar trend as far as IL-2 levels. Circulating IL-2 levels were strongly associated with the HRV L/H quotient, an index of increased sympathetic and/or decreased parasympathetic thoracic activity. A negative correlation between vagal activity (as assessed by HRV) and IL-4 occurred. Neither TNF-alpha nor IL-10 were detectable in this group of elderly patients. The results add to the concept that mood and autonomic unbalance are associated with increased systemic inflammation in old patients with decompensated CHF, a potential mechanism for mood-related worsened prognosis of heart failure at an advanced age.

Effect of Subhypnotic Doses of Dexmedetomidine on Antitumor Immunity in Mice

Dexmedetomidine, a selective alpha2 adrenergic receptor agonist, is a drug often used for sedation. Despite the high prevalence of sedating patients with tumors in intensive care settings, little is known about the effect of sedative drugs on tumor growth. We studied the effect of dexmedetomidine on antitumor immunity in mice. Subhypnotic doses of dexmedetomidine decreased interleukin (IL)-12 production from thioglycollate-induced macrophages. The treatment also decreased the ratio of the helper T lymphocytes subsets, Th1 to Th2 (Th1/Th2), in the spleen. Following subcutaneous inoculation of EL4 T-cell lymphoma cells, dexmedetomidine further decreased the splenic Th1/Th2 ratio and activity of EL4-specific cytotoxic T lymphocytes (CTLs). Finally, treatment with dexmedetomidine accelerated EL4 growth in mice. These data show that treatment of mice with subhypnotic doses of dexmedetomidine down-regulates antitumor immunity, possibly through the decreased production of IL-12 from antigen presenting cells, resulting in a Th2 shift and decreased CTL activity against EL4 in mice.

Effects of diesel on survival, growth, and gene expression in rainbow trout (Oncorhynchus mykiss) fry

Diesel spills are all too frequent disturbances of freshwater ecosystems, largely as a result of the quantities transported and consumed. Assessing the risk that such events may pose to aquatic life remains a difficult process, because of the complexity of this hydrocarbon mixture and our limited knowledge of its toxicity. A diesel spike experiment with rainbow trout (Oncorhynchus mykiss) fry was carried out to fill this knowledge gap. Survival, growth, and gene expression changes were assessed and toxicity thresholds were determined. Whereas the biological end points were consistent in the determination of (sub)lethal doses, microarrays supplied additional information on the mechanism of toxicity (oxygen deprivation) and potential long-term effects (feminization, immune system alterations) of diesel exposure on salmonids. Hemoglobins, prostaglandins, cytochromes, and gluthathion-S-transferases were among the molecular biomarkers proposed for use in future risk assessments based on microarray results. By bridging traditional toxicity testing with recent microarray technologies, this study shows the potential of genomics tools in ecotoxicity studies as well as industrial applications, including risk assessment, in the near future.

Enhancing versus Suppressive Effects of Stress on Immune Function: Implications for Immunoprotection versus Immunopathology

It is widely believed that stress suppresses immune function and increases susceptibility to infections and cancer. Paradoxically, stress is also known to exacerbate allergic, autoimmune, and inflammatory diseases. These observations suggest that stress may have bidirectional effects on immune function, being immunosuppressive in some instances and immunoenhancing in others. It has recently been shown that in contrast to chronic stress that suppresses or dysregulates immune function, acute stress can be immunoenhancing. Acute stress enhances dendritic cell, neutrophil, macrophage, and lymphocyte trafficking, maturation, and function and has been shown to augment innate and adaptive immune responses. Acute stress experienced prior to novel antigen exposure enhances innate immunity and memory T-cell formation and results in a significant and long-lasting immunoenhancement. Acute stress experienced during antigen reexposure enhances secondary/adaptive immune responses. Therefore, depending on the conditions of immune activation and the immunizing antigen, acute stress may enhance the acquisition and expression of immunoprotection or immunopathology. In contrast, chronic stress dysregulates innate and adaptive immune responses by changing the type 1-type 2 cytokine balance and suppresses immunity by decreasing leukocyte numbers, trafficking, and function. Chronic stress also increases susceptibility to skin cancer by suppressing type 1 cytokines and protective T cells while increasing suppressor T-cell function. We have suggested that the adaptive purpose of a physiologic stress response may be to promote survival, with stress hormones and neurotransmitters serving as beacons that prepare the immune system for potential challenges (eg, wounding or infection) perceived by the brain (eg, detection of an attacker). However, this system may exacerbate immunopathology if the enhanced immune response is directed against innocuous or self-antigens or dysregulated following prolonged activation, as seen during chronic stress. In view of the ubiquitous nature of stress and its significant effects on immunoprotection and immunopathology, it is important to further elucidate the mechanisms mediating stress-immune interactions and to meaningfully translate findings from bench to bedside.

Diurnal cortisol variation is associated with nocturnal blood pressure dipping

OBJECTIVE

To investigate if diurnal cortisol variation is associated with nocturnal blood pressure (BP) dipping.

METHODS

In this study, 302 healthy adults (51% female; average age 31 years) underwent 24-hour ambulatory BP assessment with BP measured randomly approximately every 20 minutes during waking hours and every hour during sleep. Salivary cortisol was obtained at five time points. Cortisol and BP have natural diurnal variations and disruptions in these diurnal variations are related to pathological conditions, such as greater risk for cardiovascular disease. A lack of a drop in cortisol from day to night and a lack of a drop in BP from waking to sleeping have both been associated with negative outcomes. It is not known, however, if diurnal variations in cortisol and BP are related, or if changes in cortisol from day to night influence BP dipping.

RESULTS

Diurnal cortisol variation was a significant predictor of BP dipping. Controlling for gender, body mass index, age, phase of menstrual cycle, sleep quality, morning cortisol, and daytime measures of the relevant cardiovascular assessments did not significantly affect the results. Cortisol variation was found to have a stronger relationship with BP dipping than any of the covariates measured.

CONCLUSION

Decreased diurnal variation in cortisol is associated with decreased diurnal variation in BP. Future studies could benefit from examining how these two variables interact in predicting disease outcomes.

Interleukin-6 production and deregulation of the hypothalamic-pituitary-adrenal axis in patients with major depressive disorders

The present study was designed to determine whether an association exists between HPA activity and cytokine production in major depression (MD). In 9 patients with MD and 11 control subjects of both sexes, all drug-free, activity of the HPA axis was evaluated by circadian rhythm of plasma cortisol, 24-h free urinary cortisol, an overnight 1 mg dexamethasone suppression test, and an oCRF stimulation test. Spontaneous and LPS-stimulated production of IL-1beta, IL-6, and TNFalpha by peripheral blood mononuclear cells were also determined. We found a significantly elevated spontaneous production of IL-6 in patients with MD (3541.2 +/- 726.8 vs 380.4 +/- 77.5 pg/mL in controls, p < 0.05), while LPS-stimulated production was significantly lower in patients than in control subjects (19,867.7 +/- 3649.2 vs 33,142.2 +/- 15,47.2 pg/mL, p < 0.05). The adrenocorticotropic hormone response to oCRF, evaluated as the area under the curve (AUCACTH) was significantly lower in patients than in control subjects (p = 0.02). A positive correlation between AUCACTH and LPS-stimulated IL-6 secretion was observed in patients with MD (r = 0.75, p < 0.05) but not in controls. These findings suggest that the activation of the inflammatory response described in depression might be associated with long-term hyperactivity of the HPA axis.

Changes in the immune system in depression and dementia: causal or coincidental effects?

Epidemiological studies show that there is a correlation between chronic depression and the likelihood of demential in later life. There is evidence that inflammatory changes in the brain are pathological features of both depression and dementia. This suggests that an increase in inflammation-induced apoptosis, together with a reductin in the synthesis of neurotrophic factors caused by a rise in brain glucocorticoids, may play a role in the pathology of these disorders. A reduction in the neuroprotective components of the kynurenine pathway, such as kynurenic acid, and an increase in the neurodegenerative components, 3-hydroxykynurenine and quinolinic acid, contribute to the pathological changes. Such changes are postulated t cause neuronal damage, and thereby predispose chronically depressed patients to demential.

Why is stress so deadly? An evolutionary perspective

The reaction of the body to prolonged stress has many harmful effects. Classical theory assumes that stress responses have evolved due to their short-term selective advantages ('flight or fight'), and despite their adverse long-term effects. In contrast, we demonstrate that the adverse effects of stress responses may have a selective advantage. Using an analytical model we show that a gene that causes the early death of a relatively unfit individual can increase in frequency in a structured population even if it has no positive effect on that individual. This result offers a new perspective on the relations between stress factors, stress responses and stress-related diseases.

Establishing an Appropriate Period of Acclimatization Following Transportation of Laboratory Animals

Stress associated with transportation has widespread effects on physiological systems in laboratory animals, including changes in the cardiovascular, endocrine, immune, central nervous, and reproductive systems. Although short-lived, these changes can confound research if animals are utilized before homeostasis is restored and physiological measures return to normal. Therefore, some period of acclimatization following transportation is generally suggested to restore homeostasis. The following two questions should be considered to establish an adequate period for acclimatization: (1) Will anticipated physiological changes confound the research to be conducted? (2) What is the length of time necessary for confounding physiological changes to normalize? Finding answers to those questions in the literature can be a challenge. Most literature on the physiological impact of transportation involves agricultural animals, although the limited literature in common laboratory animal species generally parallels changes documented in agricultural animals. The literature documents elevated heart rate and weight loss, as well as elevated concentrations of adrenaline, noradrenaline, glucose, cortisol, free fatty acids, and beta-hydroxybutyrate. Carbohydrate, protein, and lipid metabolism (both lipolysis and lipogenesis) are altered, and plasma osmolality, albumen, protein, and pack-cell volume increase. Neutrophilia and lymphopenia are also evident. These measures generally return to baseline within 1 to 7 days of transportation, although animals that are young, severely stressed, and have stress-sensitive genotypes may show altered physiological measures for several weeks. Other measures such as circadian rhythm and reproductive performance may take several weeks to months to normalize.

Stress as an endogenous adjuvant: augmentation of the immunization phase of cell-mediated immunity

Stress is thought to be immunosuppressive but paradoxically exacerbates inflammatory and autoimmune diseases. We initially showed that acute stress enhances skin immunity. Such immunoenhancement could promote immunoprotection in case of wounding, infection or vaccination but could also exacerbate immunopathological diseases. Here we identify the molecular and cellular mediators of the immunoenhancing effects of acute stress. Compared with non-stressed mice, acutely stressed animals showed significantly greater pinna swelling and leukocyte infiltration, and up-regulated macrophage chemoattractant protein-1, macrophage inflammatory protein-3alpha, IL-1alpha, IL-1beta, IL-6, tumor necrosis factor-alpha and IFN-gamma, but not IL-4 gene expression at the site of primary antigen exposure. Stressed animals also showed enhanced maturation and trafficking of dendritic cells (DCs) from skin to lymph nodes (LNs), higher numbers of activated macrophages in skin and LNs, increased T cell activation in LNs, and enhanced recruitment of surveillance T cells to skin. These findings show that important interactive components of innate (DCs and macrophages) and adaptive (surveillance T cells) immunity are mediators of the stress-induced enhancement of a primary immune response. Such enhancement during primary immunization may induce a long-term increase in immunologic memory resulting in subsequent augmentation of the immune response during secondary antigen exposure. Thus, the evolutionarily adaptive fight-or-flight stress response may protectively prepare the immune system for impending danger (e.g. infection and wounding by a predator), but may also contribute to stress-induced exacerbation of inflammatory and autoimmune diseases.

Exposure to forced swim stress alters morphofunctional characteristics of the rat thymus

The aim of this study was to investigate whether chronic stress, induced by repeated daily swimming during 21 days, alters the morphofunctional parameters in the thymus of adult rats. Our results showed that chronic stress reduced thymus mass, total number of thymocytes, volume of the thymus compartments and numerical density of thymocytes within thymus inner cortex and medulla. However, the percentage of apoptotic cells and the level of corticosterone were significantly increased. The percentages of CD4-CD8-TCRalphabeta(low/high) and CD4-CD8+TCRalphabeta(-)thymocytes were significantly increased, while the percentage of the least mature CD4+CD8-SP TCRalphabeta(-) thymocytes was significantly decreased. These results show that recurred swimming procedure induces thymus hypotrophy and elevated percentage of DN TCRalphabeta(+) cells.

Effect of propofol and isoflurane anaesthesia on the immune response to surgery

There are two major subpopulations of peripheral helper T lymphocytes: T helper 1 (Th1) and T helper 2 (Th2) cells. Surgical stress increases the number of Th2 cells, and decreases that of Th1 cells, resulting in a decrease in the Th1/Th2 ratio, and, consequently, in suppressed cell-mediated immunity. Since anaesthesia can suppress the stress response to surgery, it may inhibit the decrease in the Th1/Th2 ratio. Using flow cytometry, we studied whether propofol anaesthesia (n = 9) or isoflurane anaesthesia (n = 9) had more effect on the decrease in the Th1/Th2 ratio after surgery in patients undergoing craniotomy. The Th1/Th2 ratio decreased significantly after isoflurane anaesthesia (p = 0.011), while it did not change after propofol anaesthesia. The ratio was significantly lower with isoflurane than propofol (p = 0.009). Propofol anaesthesia attenuated the surgical stress-induced adverse immune response better than isoflurane anaesthesia.

Comparison of circulating proinflammatory cytokines and soluble apoptosis mediators in patients with chronic heart failure with versus without symptoms of depression

This clinical study compared the expression of circulating proinflammatory (tumor necrosis factor-alpha [TNF-alpha] and interleukin-6) and anti-inflammatory (interleukin-10) cytokines and soluble apoptosis mediators (Fas/Fas ligand) between patients with stable chronic heart failure and depressive symptoms (as estimated by the Zung Self-Rating Depression Scale) (n = 15) and those without these symptoms (n = 20). Patients with depressive symptoms exhibited significantly higher levels of TNF-alpha and soluble Fas ligand, as well as significantly lower levels of interleukin-10, than patients without emotional distress. A disregulated cytokine network and activated apoptosis signaling molecules may be actively implicated in the pathophysiology of chronic emotional distress and depressive symptoms in patients with heart failure.

Behavioral and neurochemical responses in mice bearing tumors submitted to social stress

Through the proinflammatory cytokines secreted in response to inflammation or injury, the immune system produces physiological and behavioral alterations. This study analyzes the effects on behavior, mononuclear proliferative response and central monoamine activity in response to the inoculation of tumor cells in mice submitted to social stress. Two groups of male OF1 mice were used, one of which was inoculated with B16 melanoma cells. Both groups were subdivided into two new groups, with one being submitted to social stress through sensory contact model with a selected aggressive subject, and the other being handled without social interaction. Subjects were exposed to social stress for a 24-h period, with three 5 min intervals of direct physical interaction, where the behavior was recorded and assessed. One hour after the stress and/or handling, they were put down and samples taken for physiological assessment. Significant behavioral changes were found in subjects with implanted tumors, mainly characterized by an increase in avoidance behavior and a decrease in immobility, defense-submission and non-social exploration behavior, coupled with an increase in the spleen mononuclear cell proliferative response. Similarly, an increase was observed in the density of dopamine(2) (D(2))-receptors in the striatum (SRT) and an increase in dopaminergic (DOPAC/DA) and serotonergic (5HIAA/5HT) turnover in the hypothalamus. The increase in the density of D(2)-receptors in the SRT coincides with the decrease in some behaviors with a predominant motor component. The results indicate significant changes in the defensive strategy used to cope with situations of intense social stress in mice bearing tumors.

Suppression of proinflammatory cytokines interleukin-1beta and tumor necrosis factor-alpha in astrocytes by a V1 vasopressin receptor agonist: a cAMP response element-binding protein-dependent mechanism

Previous research from our laboratory has demonstrated that V1 vasopressin receptor agonist (V1 agonist) induces a complex intracellular Ca2+-signaling cascade in cortical astrocytes that is initiated by G-protein-coupled V1a vasopressin receptor-mediated cytoplasmic and nuclear Ca2+ rise and converges during activation of the nuclear transcription factor cAMP response element-binding protein (CREB). In the current study, we pursued the downstream functional consequences of V1 agonist-induced Ca2+-signaling cascade for gene expression. Because astrocytes can exert immune effects analogous to immune cells in the periphery, we investigated V1 agonist regulation of cytokine gene expression in astrocytes. Results from gene array studies indicated that V1 agonist dramatically decreased the mRNA level of five cytokines. Two prominent proinflammatory cytokines, interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha), were selected for detailed analysis, and their expression was also confirmed with reverse transcriptase-PCR. Furthermore, ELISA analyses demonstrated that the peptide level of IL-1beta and TNF-alpha in the astrocyte medium was also decreased in response to V1 agonist. Using CREB antisense to determine the causal relationship between V1 agonist-induced CREB activation and suppression of IL-1beta and TNF-alpha, we demonstrated that decreased IL-1beta and TNF-alpha gene expression was dependent on upstream CREB activation. V1 agonist-induced decrease of cytokine release from cortical astrocytes was also shown to be neuroprotective in cortical neurons. To our knowledge, this is the first documentation of V1 agonist modulation of cytokine gene expression in any cell type. Implications for vasopressin as an antipyretic agent and the role of vasopressin in neurodegeneration, autoimmune diseases, stress, and neuropsychiatric behaviors are discussed.

Contrasting changes of sensitivity by lymphocytes and neutrophils to mercury in developing grey seals

Mercury is the principal metal contaminant in the St Lawrence Estuary. It impairs humoral, cellular and non-specific immune responses in many species. Since the immune system of juvenile seals is immature, it should react differently to the effects of contamination compared to that of mature animals. Phagocytosis and lymphoblastic transformation responses have been evaluated in the peripheral blood leukocytes of eight juvenile grey seals at different intervals of time over 11 weeks. Dose-response curves of 10(-9)-10(-3)M of methylmercury chloride have also been performed in vitro for evaluation of these two immune functions. The immune response of grey seals differs during their development. The phagocytosis response increased from the 2nd to 5th week post-weaning and then reached a plateau. As for the lymphoblastic transformation response, it was stable from the 2nd to the 3rd week post-weaning, increased significantly at week 4 post-weaning and then reached a plateau. These data suggest that these animals should be particularly vulnerable to infections, diseases and parasites before the 5th week post-weaning. Furthermore, mercury decreased the immune response, and age of seals had an effect on cell sensitivity to mercury. Concentrations of 10(-5)M of methylmercury chloride decreased phagocytosis and lymphoblastic transformation responses. Phagocytosis is more affected by MeHgCl contamination before this immune function reaches complete development which occurs at week 5 post-weaning. On the other hand, lymphoblastic transformation is more affected by this contaminant after its complete development which occurs at week 4 post-weaning.

Endocrine and lymphoproliferative response changes produced by social stress in mice

Daily dyadic resident-intruder encounters and uninterrupted cohabitation in pairs were used to assess the impact of different durations (5 and 15 days) of dominance and subordination experiences on splenic lymphoproliferative responses in male OF1 strain mice. HPA axis activity was assessed by measuring serum corticosterone levels, whereas splenic norepinephrine (NE) content provided a sympathetic activity index. Corticosterone levels in subordinate subjects were generally higher than in their control or dominant counterparts in both treatment paradigms. Corticosterone levels in dominant subjects were lower than in their control counterparts in both. Increasing the duration of treatments generally decreased such titers, especially so in subordinate subjects. No differences were detected in splenic NE content. Animals subjected to social interaction generally showed greater proliferation than their control counterparts. This effect was more pronounced in subordinates than dominants and after longer- rather than short-duration treatments. There was no inverse relation between proliferative responses and the subject's corticosterone levels. While corticosterone may have a general immunomodulating effect, other mediators apparently account for the effects produced by these social stress paradigms on splenic proliferative response.

Stress-induced augmentation of immune function--the role of stress hormones, leukocyte trafficking, and cytokines

Delayed-type hypersensitivity (DTH) reactions represent cell-mediated immune responses that exert important immunoprotective (resistance to viruses, bacteria, and fungi) or immunopathological (allergic or autoimmune hypersensitivity) effects. We initially utilized the skin DTH response as an experimental in vivo model to study neuro-endocrine-immune interactions in rodents. We hypothesized that just as an acute stress response prepares the cardiovascular and musculoskeletal systems for fight or flight, it may also prepare the immune system for challenges which may be imposed by a stressor. The skin DTH model allowed us to examine the effects of stress at the time of primary and secondary exposure to antigen. Studies showed that acute (2h) stress experienced before primary or secondary antigen exposure induces a significant enhancement of skin DTH. Importantly, this enhancement involved innate as well as adaptive immune mechanisms. Adrenalectomy eliminated the stress-induced enhancement of DTH. Acute administration of physiological (stress) concentrations of corticosterone and/or epinephrine to adrenalectomized animals enhanced skin DTH. Compared with controls, DTH sites from acutely stressed or hormone-injected animals showed significantly greater erythema and induration, numbers of infiltrating leukocytes, and levels of cytokine gene expression. In contrast to acute stress, chronic stress was immunosuppressive. Chronic exposure to corticosterone, or acute exposure to dexamethasone significantly suppressed skin DTH. These results suggest that during acute stress, endogenous stress hormones enhance skin immunity by increasing leukocyte trafficking and cytokine gene expression at the site of antigen entry. While these results are discussed from a mechanistic and clinical relevance perspective, it is acknowledged that much work remains to be done to elucidate the precise mechanisms mediating these bi-directional effects of stress and stress hormones and their clinical ramifications.

Maternal stress and T-cell differentiation of the developing immune system: possible implications for the development of asthma and atopy

The constant increase in asthma and atopy prevalences--despite improved treatment and knowledge of many aspects of the diseases--has raised growing concern. Accumulating evidence suggests that these increases in atopic diseases are largely attributable to environmental and lifestyle factors, and the lack of systemic childhood infections has in many studies emerged as a major factor. In addition to current high standards of hygiene and the lack or scarcity of such infections, another factor characteristic of our present-day lives could be involved. This review briefly outlines the possibility that prolonged maternal stress associated with sustained excessive cortisol secretion could affect the developing immune system--especially T(H)1/T(H)2 cell differentiation--and further increase the susceptibility to asthma and atopy in genetically predisposed individuals. This hypothesis is critically evaluated in the light of current knowledge.

Stress hormones, proinflammatory and antiinflammatory cytokines, and autoimmunity

Recent evidence indicates that glucocorticoids and catecholamines, the major stress hormones, inhibit the production of proinflammatory cytokines, such as interleukin (IL)-12, tumor necrosis factor (TNF)-alpha, and interferon (IFN)-gamma, whereas they stimulate the production of antiinflammatory cytokines, such as IL-10, IL-4, and transforming growth factor (TGF)-beta. Thus, systemically, an excessive immune response, through activation of the stress system, stimulates an important negative feedback mechanism, which protects the organism from an "overshoot" of proinflammatory cytokines and other products of activated macrophages with tissue-damaging potential. Conversely, in certain local responses and under certain conditions, stress hormones actually may boost regional immune responses, through induction of TNF-alpha, IL-1, and IL-8, and by inhibiting TGF-beta production. Therefore, conditions that are associated with significant changes in stress system activity, such as acute or chronic stress, cessation of chronic stress, severe exercise, and pregnancy and the postpartum period, through modulation of the systemic or local pro/antiinflammatory cytokine balance, may suppress or potentiate autoimmune diseases activity and/or progression.

Chronic ethanol inhibits NK cell cytolytic activity: role of opioid peptide beta-endorphin

The role of beta-endorphin (beta-EP) in ethanol-altered NK cell cytolytic activity is studied using male Fischer-344 rats as an animal model. Ethanol was administered for 1, 2, 3, or 4 wk in a liquid diet containing 8.7% ethanol (v/v), which means that 37% of the total calories were derived from ethanol. Rats treated with ethanol for 1 wk showed an increase in hypothalamic and plasma levels of immunoreactive (IR)-beta-EP, but displayed no significant effect on NK cell activity determined by (51)Cr release assay, as compared with those in pair-fed and ad libitum-fed animals. However, animals treated with ethanol for 2, 3, or 4 wk showed decreased hypothalamic and plasma levels of IR-beta-EP and decreased splenic NK cell activity. No significant decrease in the number of splenocytes and NK cells or in the percentage of NK cells was seen until after 3 and 4 wk of ethanol treatment. Exposure in vitro of splenic lymphocytes obtained from control animals to various concentrations of beta-EP increased NK cell activity. The opiate antagonist naltrexone blocked the beta-EP-stimulated effect. The in vitro NK cell response to beta-EP was reduced in the splenocytes obtained from animals treated with ethanol for 2 wk, but not in those obtained from animals treated with ethanol for 1 wk as compared with those in control animals. Additionally, beta-EP administration into the paraventricular nucleus of the hypothalamus stimulated NK cell cytolytic activity, whereas the opiate blocker administration reduced NK cell activity. The NK cell responses to paraventricular nucleus beta-EP were reduced in the animals treated with ethanol for 2 wk. These data provide evidence for the first time that ethanol inhibits NK cell cytolytic activity, possibly by reducing beta-EP-regulated splenic NK cell function.

Acute stress enhances while chronic stress suppresses skin immunity. The role of stress hormones and leukocyte trafficking

Delayed-type hypersensitivity (DTH) reactions are antigen-specific, cell-mediated immune responses that, depending on the antigen, mediate beneficial (resistance to viruses, bacteria, fungi) or harmful (allergic dermatitis, autoimmunity) aspects of immunity. Contrary to the widely held notion that stress is immunosuppressive, we have shown that under certain conditions, stress can enhance immune function. DTH reactions can be studied in rats or mice by challenging the pinnae of previously sensitized animals with antigen. Studies have shown that acute stress administered immediately before antigen exposure significantly enhances skin DTH. In contrast, chronic stress significantly suppresses skin DTH. Stress-induced changes in leukocyte distribution may contribute to these bidirectional effects of stress, since acute stress induces a significant mobilization of leukocytes from the blood to the skin, whereas chronic stress suppresses leukocyte mobilization. In order to identify the hormonal mediators of the observed effects of stress, we first showed that adrenalectomy (ADX) eliminates the stress-induced enhancement of DTH. Acute administration (to ADX animals) of low doses of corticosterone and/or epinephrine significantly enhances skin DTH. In contrast, acute administration of high doses of corticosterone, low doses of dexamethasone, or chronic administration of moderate doses of corticosterone, suppress skin DTH. Thus, the timing and duration of stress may significantly affect the nature (enhancing versus suppressive) of the effects of stress on skin immune function. These results suggest that during acute stress, stress hormones may help enhance immune function by informing the immune system about impending challenges (e.g., wounding or infection) that may be imposed by a stressor (e.g., an aggressor). Thus, during acute stress, the brain may send a warning signal to the immune system, just as it does to other fight/flight systems in the body.

Peripheral blood natural killer cell cytotoxicity after damage to the limbic system in the rat

The present work was aimed at examining the possible involvement of different parts of the septal area (dorsal, medial, lateral, and septohypothalamic nucleus), the basolateral amygdala, and the bed nucleus of the stria terminalis (BNST) in the regulation of the cytotoxic activity of NK cells (NKCC). The experimental approach included performing electrolytic (or sham) lesions in the tested brain areas and to measuring the peripheral blood NKCC (chromium-51 release assay), the number of leukocytes and lymphocytes, and the plasma corticosterone levels both before and at different time points after the lesion. Lesions were also induced in the three extralimbic structures: the paraventricular hypothalamic nucleus (PVN), the dorsal caudate-putamen, and the cerebellum. To test for a possible effect on NKCC of stress associated with blood collection, anesthesia, cranial surgery, and passing electric current through the brain the proper control experiments were also performed. Lesions of the medial septum and BNST caused gradual depression of NKCC, which peaked on the 10th day after the lesion, followed by a recovery to the baseline on days 21 (medial septum) and 42 (BNST) postinjury. In the respective sham-lesioned groups, mere insertion of electrodes into the medial septum and BNST evoked transient enhancement of NKCC (on the 3rd postlesion day), probably resulting from mechanical stimulation of the nervous tissue. Destruction of the other limbic and extralimbic structures appeared ineffective. After PVN lesions NKCC remained unchanged, despite an approximately 60% decrease in the basal corticosterone level. No adverse effects of the experimental and surgical procedures on NKCC, leukocyte and lymphocyte number, and corticosterone level were found, indicating that electrolytic lesions and other stereotaxic techniques can be safely used to study the brain-immune system interactions. The results obtained raise the question about the interrelationship between the medial septum and the hippocampal formation, BNST, the medial amygdala, and the hypothalamus (both medial and lateral) as a possible circuit involved in the regulation of cellular immune functions.

Stress-induced changes in peripheral natural killer cell cytotoxicity in pigs may not depend on plasma cortisol

The study examined cortisol (COR) involvement in stress-related changes in natural killer cell cytotoxicity (NKCC). The relationship between blood COR level, phasic changes in NKCC, and the number of large granular lymphocytes (LGL) was examined in pigs during the course of 4-h immobilization stress (IMB) and for 6 days after its termination. NKCC was determined using 18-h 51Cr-release assay, LGL number was assessed with a standard hematological method, and plasma COR level was measured by radioimmunoassay. The blood level of COR was increasing during IMB (max 446Delta% at the second hour) and decreased after its termination (max -59Delta% on day 2). Changes in NKCC level and LGL number were biphasic; i.e., an initial increase in both measures (NKCC max 24Delta%, LGL max 18Delta%) in an early phase of stress (0-1h) was followed by their subsequent decrease (NKCC max -35Delta%, LGL max -41Delta%) in the late phase (3-4 h) of stress, which persisted for several days after termination of IMB. Thus, in the early phase of stress, there was a positive correlation between NKCC, LGL number, and COR levels (all elevated); a positive correlation between the measures also occurred after termination of IMB (all decreased). A negative correlation between COR and NKCC, which might be indicative of COR-related immunosuppression, was found only in the late (3-4 h) phase of stress. It is concluded that COR may be only one of multiple factors (possibly antagonistic) determining an actual immune response during stress.

Stress and rheumatic diseases

This study was done to review the literature concerning the influence of minor and major stress factors on onset and course of rheumatoid arthritis (RA), juvenile chronic arthritis (JCA), systemic lupus erythematosus (SLE), and fibromyalgia syndrome (FS). Major life events and chronic minor stress seem to be very important factors in JCA and are significantly associated with the onset of the disease. With respect to RA and FS, stress may be a provoking factor but the data in the literature are equivocal. However, during the course of the disease, minor stress aggravates SLE, FS, JCA, and RA. Patients with FS and RA may profit from psychological therapies. Optimistic and confronting coping strategies were found most frequently and perceived to be most effective. Very important for psychological function is the social background, especially the functioning of the family is of outstanding importance for clinical and psychological outcome.

Effect of an auditory stress on peritoneal and alveolar cells in C57 BL/6J mice of advanced age

The aim of this study was to analyse the effects of auditory stress on peritoneal and alveolar macrophages in C57 BL/6J mice of advanced age, and to compare the results to those obtained in old mice submitted to a sham stress, and to those observed in young mice submitted to the same auditory stress. We used a chemiluminescence assay to measure the production of free oxygen radicals (FOR) by macrophages. Eight 22 month-old mice were exposed to a sound stress of 110 dB for three consecutive nights; nine were submitted to a sham stress. The results were compared to those obtained in young (8 week-old) mice, 21 submitted to noise stress, and 17 controls. The corticosterone level was not increased after stress in any group. FOR production in old mice was significantly higher than that in young mice. Stress did not induce significant changes in FOR production by alveolar cells in young mice; however, the FOR production by alveolar cells was significantly higher in the stressed group than in the control group of old mice. These results show that noise stress is associated with modifications of macrophage functions that are influenced by cell localization, the behaviour of alveolar and peritoneal macrophages of old mice being clearly different in our experimental model.

Neural immunoregulation: emerging roles for nerves in immune homeostasis and disease

In this review, James Downing and Jaleel Miyan outline emerging evidence for neural mechanisms that contribute to specific categories of host defence. Involvement of direct innervation in the adaptive control of immunological responses complements an established view of neuroendocrine-immune modulation. The challenge remains to understand the integrative and homeostatic functions of 'hardwiring' of peripheral immune effector sites, its bearing on disorder and potential for therapeutic modification.