Restraint stress causes tissue-specific changes in the immune cell distribution

Diurnal rhythms in peripheral blood immune cell numbers of domestic pigs

Diurnal rhythms within the immune system are considered important for immune competence. Until now, they were mostly studied in humans and rodents. However, as the domestic pig is regarded as suitable animal model and due to its importance in agriculture, this study aimed to characterize diurnal rhythmicity in porcine circulating leukocyte numbers. Eighteen pigs were studied over periods of up to 50 h. Cosinor analyses revealed diurnal rhythms in cell numbers of most investigated immune cell populations in blood. Whereas T cell, dendritic cell, and eosinophil counts peaked during nighttime, NK cell and neutrophil counts peaked during daytime. Relative amplitudes of cell numbers in blood differed in T helper cell subtypes with distinctive differentiation states. Mixed model analyses revealed that plasma cortisol concentration was negatively associated with cell numbers of most leukocyte types, except for NK cells and neutrophils. The observed rhythms mainly resemble those found in humans and rodents.

Relevance of Immune-Sympathetic Nervous System Interplay for the Development of Hypertension

Historically, the sympathetic nervous system (SNS) has been mostly associated with the 'fight or flight' response and the regulation of cardiovascular function. However, evidence over the past 30 years suggests that SNS may also influence the function of immune cells. In this review we describe the basic research being done in the area of SNS regulation of immune function. Further, we show that the SNS-immune interplay during circadian rhythm may modulate the robustness of the inflammatory response, critical for survival during periods of increased activity. Finally, new concepts of a close relationship between these systems in the pathogenesis of hypertension are discussed.

Neuroendocrine regulation of inflammation

The interaction between the sympathetic nervous system and the immune system has been documented over the last several decades. In this review, the neuroanatomical, cellular, and molecular evidence for neuroimmune regulation in the maintenance of immune homeostasis will be discussed, as well as the potential impact of neuroimmune dysregulation in health and disease.

Acute stress differently modulates β1, β2 and β3 adrenoceptors in T cells, but not in B cells, from the rat spleen

OBJECTIVES

Stress-induced rise in circulating catecholamines (CAs), followed by modulation of β-adrenergic receptors (adrenoceptors, ARs), is one of the pathways involved in the stress-mediated effects of immune functions. The spleen is an organ with a high number of lymphocytes and provides a unique microenvironment in which they reside. Thus, lymphocytes may respond differently to CAs in the spleen than in the circulation. No reports exist concerning the involvement of β-ARs in stress-mediated effects on T and B cells isolated from the spleen. Therefore, our aim was to investigate the effect of single stress exposure on gene expression and cellular localization of β-adrenoceptor subtypes in splenic T and B cells. We tried to correlate changes in adrenoceptors with the expression of apoptotic proteins.

METHODS

Immobilization (IMMO) was used as a stress model. T and B cells were isolated from rat spleen using magnetically labeled antibodies. The gene expression of individual adrenoceptors and apoptotic proteins was evaluated by real-time PCR. Immunofluorescence was used to evaluate localization and adrenoceptor expression.

RESULTS

We have found T cells to be more vulnerable to stress compared to B cells, because of increased β₁-, β₂- and β₃-ARs after a single IMMO. Moreover, β₂-ARs translocated from the nucleus to the plasma membrane in T cells after IMMO. The rise in β-ARs most probably led to the rise of Bax mRNA and Bax to Bcl-2 mRNA ratio. This might suggest the induction of an apoptotic process in T cells.

CONCLUSION

Higher susceptibility of T cells to stress via modulation of β-ARs and apoptotic proteins might shift the immune responsiveness in the spleen.

Effects of restraint stress on NALT structure and nasal IgA levels

The effects of stress on the mucosal immune responses in inflammatory disorders of the gut, as well as on salivary and intestinal IgA levels are well known. However, its effects on the structure and function of the NALT have not yet been reported, and are examined in the present study. Balb/c mice were submitted to restraint stress for 3h per day during 4 or 8d. The immunohistochemistry and flow cytometric analysis revealed that repeated restraint stress (4 and 8d) decreased the percentage, compared to the control group, of CD3(+) and CD4(+) T cells, without affecting the percentage of CD8(+) T cells or B220(+) cells (B cells). The numbers of IELs (CD4(+) and CD8(+) T cells) were lower at 4d of stress and higher at 8d. IgA(+) cells in NALT and nasal IgA levels showed a similar pattern, being significantly lower at 4d of stress and significantly higher at 8d. In summary, repeated restraint stress altered the distribution and number of lymphocytes and IgA(+) cells in nasal mucosa, probably due to changes in norepinephrine and corticosterone levels.

Acute stress-induced colonic tissue HSP70 expression requires commensal bacterial components and intrinsic glucocorticoid

Induction of heat shock protein (HSPs) has a protective effect in cells under stress. Physical stressors, such as restraint, induce HSPs in colonic tissue in vivo, but the mechanism of HSP induction is not yet clear. Because commensal bacteria support basal expression of colon epithelial HSP70, we postulated that stress responses may enhance the interaction of commensal bacteria and the colonic tissue. Restraining C57BL/6 mice for 2h effectively induced HSP70 in colonic epithelia. Both blockade of stress-induced glucocorticoid by RU486 or elimination of commensal bacteria by antibiotics independently abrogated restraint-induced HSP70 augmentation. Oral administration of LPS to commensal-depleted mice restored restraint-induced HSP70 augmentation. Because TLR4 expression was absent from the epithelial surface, and was limited to lamina propria and muscularis externa, we examined how LPS reaches the lamina propria. Alexa-LPS administered in the colonic lumen was only detected in the lamina propria of the restrained mice. Expression of the tight junction component ZO-1 in the epithelia, which regulates the passage of luminal substances through the epithelia, was reduced after restraint, but reversed by RU486. In conclusion, HSP70 induction in colonic epithelial cells under restraint requires both stress-induced glucocorticoid and luminal commensal bacteria, and LPS plays a significant role. Glucocorticoid-dependent attenuation of epithelial tight junction integrity may facilitate the access of LPS into the lamina propria, where TLR4, known to be required for HSP70 induction, is abundantly expressed. Sophisticated regulation of colonic protection against stressors involving the general stress response and the luminal environment has been demonstrated.

Sympathetic modulation of immunity: relevance to disease

Optimal host defense against pathogens requires cross-talk between the nervous and immune systems. This paper reviews sympathetic-immune interaction, one major communication pathway, and its importance for health and disease. Sympathetic innervation of primary and secondary immune organs is described, as well as evidence for neurotransmission with cells of the immune system as targets. Most research thus far has focused on neural-immune modulation in secondary lymphoid organs, has revealed complex sympathetic modulation resulting in both potentiation and inhibition of immune functions. SNS-immune interaction may enhance immune readiness during disease- or injury-induced 'fight' responses. Research also indicate that dysregulation of the SNS can significantly affect the progression of immune-mediated diseases. However, a better understanding of neural-immune interactions is needed to develop strategies for treatment of immune-mediated diseases that are designed to return homeostasis and restore normal functioning neural-immune networks.

Exercise-induced redistribution of T lymphocytes is regulated by adrenergic mechanisms

Acute exercise is known for causing considerable changes in leukocyte counts and function. In this paper we report that differentiated changes in T-lymphocyte distribution occur in lymphoid and non-lymphoid organs depending on the type and the intensity of exercise. Using fluorescent cell tracking we observed a release of T-cells from the spleen while lung, bone marrow and Peyer's patches served as target organs. The number of T-cells in the blood rose after intensive running while lymphopenia occurred after swimming exercise. Changes in number of labelled T-cells were neither found in the lymph nodes nor in the thymus regardless of exercise protocol. Following an alpha- or beta-blockade, the exercise-induced release of T-cells from the spleen and the accumulation of T-cells in the lung were inhibited while the enhancement of T-cells in the Peyer's patches was not affected. The administration of epinephrine partially mimicked the effects of exercise and resulted in a release of T-cells from both, the spleen and the liver, as well as in an increase of circulating blood T-cells. In conclusion, exercise induces a substantial re-distribution of T-cells within lymphoid and non-lymphoid organs. The migrating properties of T-cells could be partially explained by adrenergic mechanisms associated with exercise while the involvement of certain homing receptors remains to be shown. Our results suggest that the accumulation of T-cells in both, lung and Peyer's patches, may enhance the immune vigilance in these compartments which serve as the body's major defence barriers.

Effects of chronic stress on the immune response to oral human serum albumin-conjugated starch microparticles in rats

Uptake of antigens and bacteria over the follicle-associated epithelium (FAE) is increased after chronic psychological stress. We investigated whether stress affects the immune response to particle-conjugated antigens taken up via the FAE. Rats were submitted to two 10-day periods of water avoidance stress and orally immunized during these periods. Stressed immunized rats displayed altered cell populations and a Th1-skewed immune response within the lymphoid follicles, together with enhanced delayed-type hypersensitivity. We conclude that chronic stress affects the cell-mediated immune response after oral immunization, which may have implications for the understanding of allergic and autoimmune diseases and development of oral vaccines.

Acute stress reduces intraparenchymal lung natural killer cells via beta-adrenergic stimulation

There are lines of evidence that natural killer (NK) cells are sensitive to physical and psychological stress. Alterations in the immune system including NK cells are known to differ among tissues and organs. The effect of stress on the lung immune system, however, has not been well documented in spite of the fact that the lungs always confront viral or bacterial attacks as well as tumour cell metastasis. In this study, we intended to investigate the effect of restraint stress on lung lymphocytes including NK cells. C57BL/6 mice were exposed to 2 h restraint stress. The concentration of plasma epinephrine significantly rose immediately after the release from restraint as compared to home-cage control mice. Flow cytometric analysis revealed that the numbers of most lymphocyte subsets including NK cells were decreased in the lungs and blood but not in the spleen, immediately after restraint stress. Immunohistochemical examination revealed that the number of NK cells was decreased in the intraparenchymal region of the lungs, while the number of alveolar macrophages did not change. The decrease in the number of NK cells in the lungs and blood was reversed by the administration of propranolol, a nonselective beta adrenergic antagonist. Taken together, our findings suggest that acute stress reduces the number of intraparenchymal lung NK cells via activation of beta adrenergic receptors.

Intravenous catecholamine administration affects mouse intestinal lymphocyte number and apoptosis

The purposes of this study were to determine plasma and intestinal epinephrine (E) and norepinephrine (NE) concentrations in mice after exercise stress and, the effect of intravenous injection of E and NE (at concentrations during exercise) on viability of intestinal lymphocytes (IL). Exhaustive exercise significantly elevated plasma E and NE, and intestinal E, compared with sedentary animals. Twenty-four hours after intravenous NE administration, IL counts were higher (p<0.001) and % apoptotic IL were lower (p<0.001) than saline conditions. E resulted in fewer apoptotic IL at 24 h compared to saline controls. E and NE differentially influence IL numbers at 24 h after injection although both result in fewer % apoptotic IL relative to mice given saline only.

The induction of splenic suppressor T cells through an immune-privileged site requires an intact sympathetic nervous system

Antigen injection into the eye's anterior chamber (AC) induces the antigen-specific suppression of delayed-type hypersensitivity (DTH) that is mediated by NKT cells and splenic CD8+ suppressor T cells. Because the AC, uveal tissues, the thymus and spleen required to induce anterior chamber-associated immune deviation (ACAID) have dense sympathetic innervations, we examined the effects of chemical sympathectomy of mice by 6-hydroxydopamine (6-OHDA) on the induction of the suppression of contact sensitivity to trinitrophenol (TNP) induced by the injection of TNP-bovine serum albumin (BSA) into the anterior chamber. DTH measured as contact sensitivity to picrylchloride was not induced in mice that received 6-OHDA before immunization with TNP-BSA. Although spleen cells from 6-OHDA-treated TNP-BSA-immunized mice produced IFN-gamma when stimulated by TNP-BSA, the number of DTH-initiating hepatic NKT cells was reduced markedly in 6-OHDA-treated mice. Chemically denervated mice did not produce splenic suppressor T cells or thymic NKT cells that activate splenic suppressor T cells. We suggest that an intact sympathetic nervous system (SNS) is required to maintain cellular immunoregulation.

Endogenous glucocorticoids inhibit scratching behavior induced by the administration of compound 48/80 in mice

In this study, we investigated the effects of endogenous glucocorticoids on the compound 48/80 (a condensation product of N-methyl-p-methoxyphenethylamine with formaldehyde)-induced mouse scratching behavior using either RU-486 (mifepristone), a glucocorticoid receptor antagonist, or a surgical resection of the adrenal glands. Subcutaneous injection of compound 48/80 induced not only a corticosterone elevation in the plasma but also an enhanced expression of corticotropin releasing hormone (CRH) mRNA in the paraventricular nucleus, which thus suggests that hypothalamic-pituitary-adrenal axis is activated by the compound 48/80-induced cutaneous reaction. Inhibition of such an endogenous glucocorticoid activity by RU-486 significantly increased the degree of scratching behavior at not only the early-phase (<60 min) but also the late-phase (>60 min) time course after the injection of compound 48/80. Since the elevation of the histamine levels in the plasma in the RU-486-treated mice was no longer found in late-phase scratching behavior, these results thus indicate that histamine is a dominant mediator responsible for early-phase scratching behavior, while different mediators other than histamine may be also involved in the induction of late-phase scratching behavior. Moreover, surgical removal of adrenal glands also significantly increased the compound 48/80-induced scratching behavior without affecting anxiety and locomotor parameters, indicating that endogenous glucocorticoids exert their anti-pururitogenic effects independently of changes in behavioral performance. In conclusion, endogenous glucocorticoid activity was found to suppress the compound 48/80-induced scratching behavior in mice.

Social stress affects migration of blood T cells into lymphoid organs

The effect of social confrontation stress on the normal distribution of blood T cells into lymphoid organs and some other body tissues was studied. Social stress was induced by placing a male Fischer 344 (F334) rat into the home cage of a resident opponent. 51Cr-labeled blood T cells isolated from syngeneic donor, were intravenously injected into recipients immediately before confrontation. The accumulation of 51Cr-labeled T cells in the spleen, mesenteric and cervical lymph nodes 24 h after injection was about 30% lower in socially stressed than in control males. Substantially higher localization was observed in the bone marrow of socially stressed males.

Restraint stress elevates the plasma interleukin-6 levels in germ-free mice

Several recent reports demonstrated that restraint stress elevates plasma IL-6 levels; however, the precise mechanism whereby stress stimuli trigger the production of IL-6 remains to be clarified. In this study, in order to elucidate whether or not the intestinal microflora contribute to the stress-induced IL-6 elevation, the plasma IL-6 response of germ-free (GF) mice, which are indeed devoid of indigenous microflora, was compared to that of specific pathogen-free (SPF) mice. The plasma IL-6 level increased after 1 h of restraint stress and thereafter gradually decreased in GF mice as well as in SPF mice. In addition, such a stress-induced IL-6 elevation was also found in the mice reconstituted with SPF feces. The expression levels of IL-6 mRNA in the liver increased after 1 h of stress in both GF and SPF mice based on the findings of a semiquantitative RT-PCR method, although no such increase was observed in the spleen and kidney of both groups of mice. These results thus indicate that restraint stress is capable of elevating the plasma IL-6 levels independently of the intestinal microflora and the liver is one of the main sources responsible for the increased plasma IL-6 during stress.

Quantitative analysis of the neuroendocrine-immune axis: linear modeling of the effects of exogenous corticosterone and restraint stress on lymphocyte subpopulations in the spleen and thymus in female B6C3F1 mice

The effects of exogenous corticosterone and restraint stress on the number and percentage of lymphocyte subpopulations in the spleen and thymus were evaluated. The data were used to generate linear models that describe the relationship between these parameters and the area under the corticosterone concentration vs time curve (AUC). Comparison of the models revealed that the number of nucleated cells in the spleen was decreased similarly by exogenous corticosterone and restraint (at equivalent corticosterone AUC values). However, exogenous corticosterone caused a greater decrease in cell number in the thymus than it did in the spleen. Corticosterone preferentially depleted CD4+CD8+ cells in the thymus, whereas the same corticosterone exposure produced by restraint stress did not. In the spleen, cell number for all major cell types was decreased by both treatments, but there were minor differences in the change in percentage of some subpopulations induced by exogenous corticosterone as compared to restraint. The models derived here provide quantitative data that indicate the magnitude of corticosterone and stress-induced effects on lymphocyte populations in the spleen and thymus. These results have mechanistic implications, and they may be useful in future efforts to extrapolate from mouse to human by completing a risk assessment parallelogram.

Nicotine attenuates stress-induced changes in plasma amino acid concentrations and locomotor activity in rats

It is known that stressor stimuli (both systemic and processive) and nicotine activate central nervous system. Surprisingly, numerous studies have demonstrated an increase in nicotine self-administration among smokers when exposed to stress in order to reduce the stress-related tension. Therefore, in the present study, we decided to investigate the influence of nicotine on both behavioral (i.e., on locomotor activity) and metabolic (i.e., on the level of amino acids in the plasma) changes following water immersion restraint stress in rats. As expected, the stress produced evident decline in locomotor activity of the rats (p < 0.001) and in the levels of all plasma amino acids studied (p < 0.05). Nicotine alone also significantly reduced locomotor activity (p < 0.05) and the levels of some plasma amino acids. However, when administered to rats subjected to water immersion and restraint, nicotine attenuated both stress-induced decrease in locomotor activity (p < 0.05) and in some plasma amino acids. Thus, this study demonstrated that the mode of action of nicotine is strongly dependent on the level of initial brain activity, which provide new evidence for arousal-modulation model of nicotine action.