Sympathetic nervous system interaction with the immune system

Immunology of Stress: A Review Article

Stress significantly impacts the immune system, affecting susceptibility to illness and overall health. This review examines the intricate relationship between stress and the immune system, offering insights having practical implications for health and disease prevention. Stress can significantly trigger molecular and immune modulation, affecting the distribution and trafficking of immune cells in various organs and altering their composition in the blood. The review delves into two key pathways connecting stress and immunity: the hypothalamic-pituitary-adrenal (HPA) axis and the sympathetic nervous system. Stress activates the neuroendocrine system and triggers microglia in the brain, releasing stress hormones and neurotransmitters that modulate the function and movement of immune cells. Acute stress can temporarily strengthen immunity and promote protection during infection; in contrast, chronic stress dysregulates or inhibits immune functions. Chronic stress causes an increase in cortisol levels through the HPA axis, ultimately suppressing the immune response. Recognizing stress triggers and implementing effective stress management techniques can significantly impact individuals' well-being. This review indicates that immune cells express genes differentially in response to stress, suggesting individual variabilities in the immune response against stress. This underscores the need for a personalized approach to stress management. This review also highlights the potential link between chronic stress and autoimmune disorders and warrants further investigation.

The Potential Mechanisms of High-Velocity, Low-Amplitude, Controlled Vertebral Thrusts on Neuroimmune Function: A Narrative Review

The current COVID-19 pandemic has necessitated the need to find healthcare solutions that boost or support immunity. There is some evidence that high-velocity, low-amplitude (HVLA) controlled vertebral thrusts have the potential to modulate immune mediators. However, the mechanisms of the link between HVLA controlled vertebral thrusts and neuroimmune function and the associated potential clinical implications are less clear. This review aims to elucidate the underlying mechanisms that can explain the HVLA controlled vertebral thrust--neuroimmune link and discuss what this link implies for clinical practice and future research needs. A search for relevant articles published up until April 2021 was undertaken. Twenty-three published papers were found that explored the impact of HVLA controlled vertebral thrusts on neuroimmune markers, of which eighteen found a significant effect. These basic science studies show that HVLA controlled vertebral thrust influence the levels of immune mediators in the body, including neuropeptides, inflammatory markers, and endocrine markers. This narravtive review discusses the most likely mechanisms for how HVLA controlled vertebral thrusts could impact these immune markers. The mechanisms are most likely due to the known changes in proprioceptive processing that occur within the central nervous system (CNS), in particular within the prefrontal cortex, following HVLA spinal thrusts. The prefrontal cortex is involved in the regulation of the autonomic nervous system, the hypothalamic-pituitary-adrenal axis and the immune system. Bi-directional neuro-immune interactions are affected by emotional or pain-related stress. Stress-induced sympathetic nervous system activity also alters vertebral motor control. Therefore, there are biologically plausible direct and indirect mechanisms that link HVLA controlled vertebral thrusts to the immune system, suggesting HVLA controlled vertebral thrusts have the potential to modulate immune function. However, it is not yet known whether HVLA controlled vertebral thrusts have a clinically relevant impact on immunity. Further research is needed to explore the clinical impact of HVLA controlled vertebral thrusts on immune function.

Genetic ablation of bone marrow beta-adrenergic receptors in mice modulates miRNA-transcriptome networks of neuroinflammation in the paraventricular nucleus

Elucidating molecular pathways regulating neuroimmune communication is critical for therapeutic interventions in conditions characterized by overactive immune responses and dysfunctional autonomic nervous system. We generated a bone marrow-specific adrenergic beta 1 and beta 2 knockout mouse chimera (AdrB1.B2 KO) to determine how sympathetic drive to the bone affects transcripts and miRNAs in the hypothalamic paraventricular nucleus (PVN). This model has previously exhibited a dampened systemic immune response and decreased blood pressure compared with control animals. Reduced sympathetic responsiveness of the bone marrow hematopoietic cells of AdrB1.B2 KO chimera led to suppression of transcriptional networks that included leukocyte cell adhesion and migration and T cell-activation and recruitment. Transcriptome responses related to IL-17a signaling and the renin-angiotensin system were also suppressed in the PVN. Based on the transcriptome response, we next computationally predicted miRNAs in the PVN that may underscore the reduced sympathetic responsiveness of the bone marrow cells. These included miR-27b-3p, miR-150, miR-223-3p, and miR-326. Using real-time PCR, we measured a downregulation in the expression of miR-150-5p, miR-205-5p, miR-223-3p, miR-375-5p, miR-499a-5p, miR-27b-3p, let-7a-5p, and miR-21a-5p in the PVN of AdrB1.B2 KO chimera, confirming computational predictions that these miRNAs are associated with reduced neuro-immune responses and the loss of sympathetic responsiveness in the bone marrow. Intriguingly, directional responses of the miRNA corresponded to mRNAs, suggesting complex temporal or circuit-dependent posttranscriptional control of gene expression in the PVN. This study identifies molecular pathways involved in neural-immune interactions that may act as targets of therapeutic intervention for a dysfunctional autonomic nervous system.

Is the Cerebellum Involved in the Nervous Control of the Immune System Function?

BACKGROUND

According to the views of psychoneuroendocrinoimmunology, many interactions exist between nervous, endocrine and immune system the purpose of which is to achieve adaptive measures restoring an internal equilibrium (homeostasis) following stress conditions. The center where these interactions converge is the hypothalamus. This is a center of the autonomic nervous system that controls the visceral systems, including the immune system, through both the nervous and neuroendocrine mechanisms. The nervous mechanisms are based on nervous circuits that bidirectionally connect hypothalamic neurons and neurons of the sympathetic and parasympathetic system; the neuroendocrine mechanisms are based on the release by neurosecretory hypothalamic neurons of hormones that target the endocrine cells and on the feedback effects of the hormones secreted by these endocrine cells on the same hypothalamic neurons. Moreover, the hypothalamus is an important subcortical center of the limbic system that controls through nervous and neuroendocrine mechanisms the areas of the cerebral cortex where the psychic functions controlling mood, emotions, anxiety and instinctive behaviors take place. Accordingly, various studies conducted in the last decades have indicated that hypothalamic diseases may be associated with immune and/or psychic disorders.

OBJECTIVE

Various researches have reported that the hypothalamus is controlled by the cerebellum through a feedback nervous circuit, namely the hypothalamocerebellar circuit, which bi-directionally connects regions of the hypothalamus, including the immunoregulatory ones, and related regions of the cerebellum. An objective of the present review was to analyze the anatomical bases of the nervous and neuroendocrine mechanisms for the control of the immune system and, in particular, of the interaction between hypothalamus and cerebellum to achieve the immunoregulatory function.

CONCLUSION

Since the hypothalamus represents the link through which the immune functions may influence the psychic functions and vice versa, the cerebellum, controlling several regions of the hypothalamus, could be considered as a primary player in the regulation of the multiple functional interactions postulated by psychoneuroendocrinoimmunology.

Stress and catecholamines modulate the bone marrow microenvironment to promote tumorigenesis

High vascularization and locally secreted factors make the bone marrow (BM) microenvironment particularly hospitable for tumor cells and bones to a preferred metastatic site for disseminated cancer cells of different origins. Cancer cell homing and proliferation in the BM are amongst other regulated by complex interactions with BM niche cells (e.g. osteoblasts, endothelial cells and mesenchymal stromal cells (MSCs)), resident hematopoietic stem and progenitor cells (HSPCs) and pro-angiogenic cytokines leading to enhanced BM microvessel densities during malignant progression. Stress and catecholamine neurotransmitters released in response to activation of the sympathetic nervous system (SNS) reportedly modulate various BM cells and may thereby influence cancer progression. Here we review the role of catecholamines during tumorigenesis with particular focus on pro-tumorigenic effects mediated by the BM niche.

Deletion of muscarinic type 1 acetylcholine receptors alters splenic lymphocyte functions and splenic noradrenaline concentration

The existence of interactions between the immune and the sympathetic nervous systems is well established. Noradrenaline can promote or inhibit the immune response, and conversely, the immune response itself can affect noradrenaline concentration in lymphoid organs, such as the spleen. It is also well known that acetylcholine released by pre-ganglionic neurons can modulate noradrenaline release by the postsynaptic neuron. The spleen does not receive cholinergic innervation, but it has been reported that lymphocytes themselves can produce acetylcholine, and express acetylcholine receptors and acetylcholinesterase. We found that the spleen of not overtly immunized mice in which muscarinic type 1 acetylcholine receptors have been knocked out (M1KO) has higher noradrenaline concentrations than that of the wildtype mice, without comparable alterations in the heart, in parallel to a decreased number of IgG-producing B cells. Splenic lymphocytes from M1KO mice displayed increased in vitro-induced cytotoxicity, and this was observed only when CD4(+) T cells were present. In contrast, heterozygous acetylcholinesterase (AChE+/-) mice, had no alterations in splenic noradrenaline concentration, but the in vitro proliferation of AChE+/- CD4(+) T cells was increased. It is theoretically conceivable that reciprocal effects between neuronally and non-neuronally derived acetylcholine and noradrenaline might contribute to the results reported. Our results emphasize the need to consider the balance between the effects of these mediators for the final immunoregulatory outcome.

Acute psychosocial stress induces differential short-term changes in catecholamine sensitivity of stimulated inflammatory cytokine production

BACKGROUND

We have previously shown that psychosocial stress induces acute changes in glucocorticoid (GC) sensitivity of pro-inflammatory cytokine production. However, hormones of the sympathetic adrenal medullary system complement endocrine regulation of inflammatory responses. The current study therefore aimed at investigating the effects of repeated acute stress exposure on catecholamine sensitivity of inflammatory cytokine production.

METHODS

Twenty healthy male participants were subjected to the Trier Social Stress Test on two consecutive days. Blood samples were taken before and repeatedly after stress. Whole blood was stimulated with lipopolysaccharide and incubated with increasing concentrations of epinephrine (E) and norepinephrine (NE) for 18h. Tumor-necrosis-factor (TNF) alpha and interleukin (IL)-6 were measured in culture supernatants.

RESULTS

Overall, incubation with E and NE induced dose-dependent suppression of TNF-alpha (NE: F=77.66, p<.001; E: F=63.38, p<.001), and IL-6 production (NE: F=28.79, p<.001; E: F=24.66, p<.001). Acute stress exposure resulted in reduced sensitivity of TNF-alpha (NE: F=6.36, p<.001; E: F=4.86, p=.005), but not IL-6 (NE: F=1.07, p=.38; E: F=0.88, p=.50) to the inhibitory signals of E and NE. No evidence of habituation of these effects was found (all p⩾.22).

CONCLUSIONS

The present findings extend our knowledge on changes in inflammatory target tissue sensitivity in response to acute psychosocial stress from glucocorticoid-dependent effects to catecholamine-dependent effects. Stress-induced decreases in catecholamine sensitivity thereby suggest intracellular processes aiding in maintaining a healthy endocrine-immune interplay. Longitudinal studies will have to investigate the processes leading from a supposedly beneficial short-term catecholamine resistance in response to acute stress to basal catecholamine resistance observed in relation to negative health outcomes.

Nicotinic receptor Alpha7 expression during mouse adrenal gland development

The nicotinic acetylcholine receptor alpha 7 (α7) is a ligand-activated ion channel that contributes to a diversity of cellular processes involved in development, neurotransmission and inflammation. In this report the expression of α7 was examined in the mouse developing and adult adrenal gland that expresses a green fluorescent protein (GFP) reporter as a bi-cistronic extension of the endogenous α7 transcript (α7(G)). At embryonic day 12.5 (E12.5) α7(G) expression was associated with the suprarenal ganglion and precursor cells of the adrenal gland. The α7(G) cells are catecholaminergic chromaffin cells as reflected by their progressive increase in the co-expression of tyrosine hydroxylase (TH) and dopamine-beta-hydroxylase (DBH) that is complete by E18.5. In the adult, α7(G) expression is limited to a subset of chromaffin cells in the adrenal medulla that cluster near the border with the adrenal cortex. These chromaffin cells co-express α7(G), TH and DBH, but they lack phenylethanolamine N-methyltransferase (PNMT) consistent with only norepinephrine (NE) synthesis. These cell groups appear to be preferentially innervated by pre-ganglionic afferents identified by the neurotrophin receptor p75. No afferents identified by beta-III tubulin, neurofilament proteins or p75 co-expressed α7(G). Occasional α7(G) cells in the pre-E14.5 embryos express neuronal markers consistent with intrinsic ganglion cells and in the adult some α7(G) cells co-express glutamic acid decarboxylase. The transient expression of α7 during adrenal gland development and its prominent co-expression by a subset of NE chromaffin cells in the adult suggests that the α7 receptor contributes to multiple aspects of adrenal gland development and function that persist into adulthood.

Modulation of immune function by glutamatergic neurons in the cerebellar interposed nucleus via hypothalamic and sympathetic pathways

Our recent work has shown that the cerebellar interposed nucleus (IN) contains glutamatergic neurons that send axons directly to the hypothalamus. In the present study, we aimed to demonstrate modulation of cellular and humoral immunity by glutamatergic neurons in the cerebellar IN by means of gene interventions of glutaminase (GLS), an enzyme for glutamate synthesis, and to reveal pathways transmitting the immunomodulation. Injection of GLS-shRNA lentiviral vector into bilateral cerebellar IN downregulated GLS expression in the IN. The silencing of GLS gene in the cerebellar IN decreased interleukin (IL)-2 and interferon (IFN)-γ production, B-cell number, and IgM antibody level in response to antigen bovine serum albumin (BSA). On the contrary, injection of GLS lentiviral vector into bilateral cerebellar IN upregulated GLS expression in the IN. The GLS gene overexpression in the IN caused opposite immune effects to the GLS gene knockdown. Simultaneously, the GLS gene silencing in the cerebellar IN reduced and the GLS overexpression elevated glutamate content in the hypothalamus, but they both did not affect glycine and GABA contents in the hypothalamus. In addition, the immune changes caused by the GLS gene interventions in the IN were accompanied by alteration in norepinephrine content in the spleen and mesenteric lymph nodes but not by changes in adrenocortical and thyroid hormone levels in serum. These findings indicate that glutamatergic neurons in the cerebellar IN regulate cellular and humoral immune responses and suggest that such immunoregulation may be conveyed by cerebellar IN-hypothalamic glutamatergic projections and sympathetic nerves that innervate lymphoid tissues.

Learned placebo responses in neuroendocrine and immune functions

The phenomenon of learned placebo responses in neuroendocrine and immune functions is a fascinating example of communication between the brain and both the endocrine and peripheral immune systems. In this chapter, we will give a short overview of afferent and efferent communication pathways, as well as the central mechanisms, which steer the behavioral conditioned immune response. Subsequently, we will focus on data that provides evidence for learned immune responses in experimental animals and learned neuroendocrine and immune placebo responses in humans. Finally, we will take a critical look at these learning protocols, to determine whether or not they can be considered a viable additional treatment option to pharmacological regimens in clinical routine. This is fundamental, since there are still a number of issues, which need to be solved, such as the potential reproducibility, predictability, and extinction of the learned neuroendocrine and immune responses. Together, these findings not only provide an excellent basis to increase our understanding of human biology but may also have far reaching clinical implications. They pave the way for the ultimate aim of employing associative learning protocols as supportive treatment strategies in pharmacological regimens. As a result, medication levels may be reduced, as well as their unwanted side effects, providing a maximized therapeutic outcome to the benefit of the patient.

Tyrosine hydroxylase expression in CD4(+) T cells is associated with joint inflammatory alleviation in collagen type II-induced arthritis

We have recently reported that CD4(+) T cells synthesize and secrete catecholamines that facilitate a shift of T helper 1 (Th1)/Th2 balance toward Th2 polarization. In this study, we used an animal model of human rheumatoid arthritis, collagen type II-induced arthritis (CIA), to explore relationship between catecholamine production in CD4(+) T cells and Th1-/Th2-mediated joint inflammation. Histopathological observation of ankle joints of CIA mice displayed an evident inflammatory change on day 35 and a major damage to bones on day 55 post-immunization. Expression of Th1-specific transcription factor, T-bet, and cytokines, IL-2 and IFN-γ, and Th2-specific transcription factor, GATA-3, and cytokines, IL-4 and IL-10, was all upregulated on days 35 and 55 post-immunization, but the elevated Th1 response tended to decrease and the enhanced Th2 response tended to increase with the CIA progression. Expression of tyrosine hydroxylase (TH), a rate-limiting enzyme for synthesis of catecholamines, dramatically increased in ankle joints of CIA mice, although this increase was reduced on day 55 relative to that on day 35 post-immunization. In synovial tissue of CIA ankle joints but not normal joints, CD4-, T-bet-, GATA-3-, and TH-immunoreactive cells were found. Importantly, co-expressed cells with CD4 and TH, T-bet and TH, and GATA-3 and TH were observed in synovial tissue of CIA ankle joints. These results suggest that an increase in catecholamine production occurs in inflamed joints of CIA. The catecholamines are, at least in part, from Th1 and Th2 cells, and they may be related to joint inflammatory alleviation in CIA progression.

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.).

Cerebellar fastigial nuclear GABAergic projections to the hypothalamus modulate immune function

Our previous work has shown that the cerebellar fastigial nucleus (FN) is involved in modulation of lymphocyte function. Herein, we investigated effect of FN γ-aminobutyric acid (GABA)-ergic projections to the hypothalamus on lymphocytes to understand pathways and mechanisms underlying cerebellar immunomodulation. By injection of Texas red dextran amine (TRDA), an anterograde tracer, into FN, we found that the TRDA-labeled fibers from the FN traveled through the superior cerebellar peduncle (SCP), crossed in decussation of SCP (XSCP), entered the hypothalamus, and primarily terminated in the lateral hypothalamic area (LHA). Further, by injecting Fluoro-Ruby (FR), a retrograde tracer, in LHA, we observed that the FR-stained fibers retrogradely passed through XSCP and reached FN. Among these FR-positive neurons in the FN, there were GABA-immunoreactive cells. We then microinjected vigabatrin, which is an inhibitor of GABA-transaminase (GABA-T) that degrades GABA, bilaterally into FN. The vigabatrin treatment increased both number of GABA-immunoreactive neurons in FN-LHA projections and GABA content in the hypothalamus. Simultaneously, vigabatrin significantly reduced concanavalin A (Con A)-induced lymphocyte proliferation, anti-sheep red blood cell (SRBC) IgM antibody level, and natural killer (NK) cell number and cytotoxicity. In support of these findings, we inhibited GABA synthesis by using 3-mercaptopropionic acid (3-MP), which antagonizes glutamic acid decarboxylase (GAD). We found that the inhibition of GABA synthesis caused changes that were opposite to those when GABA was increased with vigabatrin. These findings show that the cerebellar FN has a direct GABAergic projection to the hypothalamus and that this projection actively participates in modulation of lymphocytes.

Adverse childhood experiences are associated with migraine and vascular biomarkers

OBJECTIVES

Migraine is a risk factor for stroke in young women. Biomarker studies implicate endothelial activation as a possible mechanism. Emerging relationships of childhood adversity with migraine, and with inflammation, a component of endothelial activation, suggest that it may play a role in the migraine-stroke association. Our objective is to evaluate the relationship between adverse childhood experiences (ACEs), migraine, and vascular biomarker levels in premenopausal women.

METHODS

Vascular and metabolic biomarkers from women 18-50 years, including 125 with migraine (interictal) and 50 without migraine, were evaluated. An ACE questionnaire was later collected by mail (response rate 80.6%, 100 migraineurs, 41 controls).

RESULTS

Migraineurs and controls were demographically similar. Migraineurs reported adversity more commonly than controls (71% vs 46%, odds ratio [OR] = 1.53, 95% confidence interval 1.07-2.17). Average ACE scores were elevated in migraineurs as compared with controls (2.4 vs 0.76, P < .001). ACE scores correlated with headache frequency (0.37, P = .001) and younger age of headache onset (-0.22, P = .04). It also correlated with body mass index (r = 0.43, P = .0001), von Willebrand factor activity (r = 0.21, P = .009), tissue plasminogen activator antigen (r = 0.28, P = .004), prothrombin activation fragment (r = 0.36, P = .001), high-sensitivity C-reactive protein (r = 0.98, P = .0001), transforming growth factor-beta1 (r = 0.28, P = .003), tissue necrosis factor-alpha (r = 0.20, P = .03), interleukin-6 (r = 0.22, P = .03), adiponectin (r = -0.29, P = .003), and nitrate/nitrite concentration (r = -314, P = .001). Logistic regression analyses (adjusted for vascular risk factors and migraine) demonstrated an association of childhood adversity with inflammatory factors (high-sensitivity C-reactive protein, interleukin-6, and tissue necrosis factor-alpha).

CONCLUSIONS

In young women, adverse childhood events are associated with migraine, particularly chronic and transformed migraine, and with vascular biomarkers, especially inflammatory biomarkers. These findings implicate early life stress as a link between migraine and endothelial activation.

Stress and the anti-influenza immune response: repeated social defeat augments clonal expansion of CD8(+)T cells during primary influenza A viral infection

Social disruption stress (SDR) prior to primary influenza A virus (IAV) infection augments memory to IAV re-challenge in a T cell-specific manner. However, the effect of SDR on the primary anti-viral immune response has not been elucidated. In this study, SDR-infected (INF) mice terminated viral gene expression earlier and mounted an enhanced pulmonary IAV-specific CD8(+)T cell response versus controls. Additionally, SDR-INF mice had a more pro-inflammatory lung profile prior to and during infection and an attenuated corticosterone response. These data demonstrate neuroendocrine modification of the lung microenvironment and increased antigen-specific T cell activation, clonal expansion and viral control in stress-exposed mice.

Modulation of immune responses in stress by Yoga

Stress is a constant factor in today's fastpaced life that can jeopardize our health if left unchecked. It is only in the last half century that the role of stress in every ailment from the common cold to AIDS has been emphasized, and the mechanisms involved in this process have been studied. Stress influences the immune response presumably through the activation of the hypothalamic-pituitary adrenal axis, hypothalamic pituitary-gonadal axis, and the sympathetic-adrenal-medullary system. Various neurotransmitters, neuropeptides, hormones, and cytokines mediate these complex bidirectional interactions between the central nervous system (CNS) and the immune system. The effects of stress on the immune responses result in alterations in the number of immune cells and cytokine dysregulation. Various stress management strategies such as meditation, yoga, hypnosis, and muscle relaxation have been shown to reduce the psychological and physiological effects of stress in cancers and HIV infection. This review aims to discuss the effect of stress on the immune system and examine how relaxation techniques such as Yoga and meditation could regulate the cytokine levels and hence, the immune responses during stress.

Psychological stress is associated with relapse in type 1 autoimmune hepatitis

BACKGROUND/AIM

The pathophysiological basis of relapse and recrudescence in type 1 autoimmune hepatitis (AIH) is poorly understood. This study examined factors associated with biochemical relapse in type 1 AIH, and specifically addressed whether psychological stress was associated with a relapsing-remitting disease course.

METHODS

A case-control study design was used to analyse 33 patients with AIH followed at the Yale Liver Clinic during a 4-year period. Twenty-two patients with 46 episodes of relapse or recrudescence (cases) and 11 controls in long-term remission were identified during this period. Clinical variables were collected to establish factors associated with relapse. All patients were administered the Social Readjustment Rating Scale (SRRS), a psychological stress questionnaire consisting of 43 weighted life events. Stress is judged to be low when the score is 0-150; mild, 151-200; moderate, 201-300 and major >300.

RESULTS

AST, ALT, prednisone dose and SRRS score were all significantly different between cases and controls. The mean SRRS score for cases with relapse/recrudescence was 239 vs 152 for the control group, P=0.048 and remained significant on ancova analysis which accounted for covariables, P=0.05. Cases also identified additional stressors not represented in the SRRS at a significantly higher rate than controls. Conversely, the controls spontaneously identified coping strategies that may have allowed them to manage stress more effectively.

CONCLUSION

Psychological stress is a significant factor that is associated with relapse in type 1 autoimmune hepatitis. Management of AIH may benefit from strategies to reduce stress and promote psychological well being.

Connecting chronic and recurrent stress to vascular dysfunction: no relaxed role for the renin-angiotensin system

The renin-angiotensin system (RAS) is classically considered to be a protective system for volume balance and is activated during states of volume depletion. Interestingly, one of the major pathways activating the system is the sympathetic nervous system, also the primary mediator of the acute stress response. When one further examines the cells mediating the immune site of the response, which is primarily an inflammatory response leading to defense at a locally injured area, these cells all express the ANG II type 1 receptor (AGTR1). Scattered throughout the literature are reports indicating that acute and chronic stress can activate renin and increase plasma levels of components of the RAS. Moreover, there are reports describing that ANG II can modulate the distribution and function of immune cells. Since the inflammatory response is also implicated to be central in the initiation and progression of vascular damage, we propose in this review that recurrent acute stress and chronic stress can induce a state with inflammation, due to ANG II-mediated activation of inflammatory cells, specifically monocytes and lymphocytes. Such a proposal would explain a lot of the observations regarding RAS components in inflammatory cells. Despite its attractiveness, substantial research in this area would be required to substantiate this hypothesis.

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.

Does caffeine reverse the EAC cell-induced immune suppression?

The aim of this study was to investigate the effect of long-term consumption of caffeine in the development of Ehrlich ascites carcinoma (EAC) cells in adult female mice, 25–30 g, in relation to immune response. Mice were treated with caffeine (20 mg kg−1 daily, p.o.) for 22–27 consecutive days or inoculated with EAC cells (5 times 106 cells/mL, i.p.), or both. Control mice, corresponding to experimental groups, were treated with corresponding vehicles under similar conditions. The lymphocyte viability, mitogen-induced proliferating activity, cytotoxicity and DNA fragmentation from blood, spleen and thymus of both control and experimental groups were measured as immune response parameters. An immune response index, corticosterone, was also measured in adrenals and plasma under similar conditions. Results showed that development of EAC cells caused immune suppression with a reduction of lymphocyte viability, cytotoxicity and proliferative activity and induction of DNA fragmentation in those tissues, as well as an increase in plasma corticosterone. Though long-term caffeine treatment (which resulted in tolerance to caffeine) alone did not alter significantly any of the immune response parameters studied, including corticosterone status (immune biomarker), the continuation of caffeine treatment during the development of EAC cells either restored or reduced the EAC cell-induced alteration in these parameters, including the HPA axis biomarker. These results suggest that long-term caffeine intake may inhibit or reverse the EAC cell-induced immune suppression.

Improving survival rates in two models of spontaneous postoperative metastasis in mice by combined administration of a beta-adrenergic antagonist and a cyclooxygenase-2 inhibitor

Clinical practice does not consider perioperative paracrine and neuroendocrine stress responses as risk factors for cancer recurrence, although recent animal studies provided supportive evidence. Suggested mechanisms include the effects of stress-hormones on tumor cells and on host physiology. In this study, in mice undergoing primary tumor excision, we tested the survival-enhancing potential of perioperative blockade of catecholamines and prostaglandins, and studied potential mediating mechanisms. C57BL/6J mice were inoculated intrafootpad with syngeneic B16F10.9-melanoma or Lewis lung carcinoma, and the paw was amputated when a developing tumor exceeded 100 microl. The clinically used beta-adrenergic antagonist propranolol, and/or the cyclooxygenase-2 inhibitor etodolac, were administered once before amputation, and recurrence-free survival was monitored. In different studies, NK cytotoxicity, leukocytes' molecular functional markers, and vascular endothelial growth factor secretion by tumor cells were studied in the context of surgery and drug treatments. The findings indicated that the combination of propranolol and etodolac, but neither drug alone, significantly and markedly improved survival rates in both tumor models, and was as effective as established immunostimulatory agents (IL-12 and polyinosinic-polycytiylic acid). Surgery markedly reduced NK cytotoxicity and NK cell expression of Fas ligand and CD11a, reduced all circulating lymphocyte-subtype concentrations, and increased corticosterone levels. Propranolol and etodolac administration counteracted these perturbations. B16 and 3LL secreted vascular endothelial growth factor in vitro, but secretion was not affected by catecholamine agonists, prostaglandins, corticosterone, propranolol, or etodolac. Overall, propranolol and etodolac administration, which could be applied perioperatively in most cancer patients with minimal risk and low cost, has counteracted several immunologic and endocrinologic perturbations and improved recurrence-free survival rates in mice undergoing primary tumor excision.

The learned immune response: Pavlov and beyond

The ability to associate physiological changes with a specific flavor was most likely acquired during evolution as an adaptive strategy aimed at protecting the organism while preparing it for danger. The behaviorally conditioned or learned immune response is an exquisite example of the bidirectional communication between the central nervous system (CNS) and the peripheral immune system. How is it possible that specific immuno-modulating properties of a drug or substance (unconditioned stimulus) can be re-enlisted just by the mere re-exposure to a particular taste, odor or environment (conditioned stimulus)? To answer this key question, we review the neurobiological mechanism mediating this type of associative learning, as well as the pathways and mechanisms employed by the brain to harness the immune system during the execution of the conditioned immune response. Finally, we focus on the potential therapeutic relevance of such learned immune responses, and their re-conceptualization within the framework of "learned placebo effects".

Influenza virus-specific immunological memory is enhanced by repeated social defeat

Immunological memory (MEM) development is affected by stress-induced neuroendocrine mediators. Current knowledge about how a behavioral interaction, such as social defeat, alters the development of adaptive immunity, and MEM is incomplete. In this study, the experience of social disruption stress (SDR) prior to a primary influenza viral infection enhanced the frequency and function of the T cell memory pool. Socially stressed mice had a significantly enlarged population of CD8(+) T cells specific for the immunodominant NP366-74 epitope of A/PR/8/34 virus in lung and spleen tissues at 6-12 wk after primary infection (resting memory). Moreover, during resting memory, SDR-MEM mice responded with an enhanced footpad delayed-type hypersensitivity response, and more IFN-gamma-producing CD4(+) T cells were detected after ex vivo stimulation. When mice were rechallenged with A/PR/8/34 virus, SDR-MEM mice terminated viral gene expression significantly earlier than MEM mice and generated a greater D(b)NP(366-74)CD8(+) T cell response in the lung parenchyma and airways. This enhancement was specific to the T cell response. SDR-MEM mice had significantly attenuated anti-influenza IgG titers during resting memory. Similar experiments in which mice were primed with X-31 influenza and challenged with A/PR/8/34 virus elicited similar enhancements in the splenic and lung airway D(b)NP(366-74)CD8(+) T cell populations in SDR-MEM mice. This study demonstrates that the experience of repeated social defeat prior to a primary viral infection significantly enhances virus-specific memory via augmentation of memory T cell populations and suggests that social stressors should be carefully considered in the design and analysis of future studies on antiviral immunity.

Stress, immunity and skin collagen integrity: evidence from animal models and clinical conditions

The skin is the largest organ of the human body and plays a major role in maintaining homeostasis and protection. As the main component of skin, collagen has a key role in providing integrity and elasticity to this organ. Several factors, including autoimmune disease, aging, and stress, can change the quantity and integrity of skin collagen. These factors impair collagen quality and consequently affect skin function. Stress seems to affect the integrity of skin collagen through glucocorticoid-mediated processes that alter its synthesis and degradation. Glucocorticoids also affect skin quality through modulation of the immune system. This review will briefly present comprehensive data from both animal and human studies delineating processes that modulate alterations in collagen in general, and will treat in more detail the consequences of stress on skin collagen.

New insights into cytokine gene expression in the rat hypothalamus following endotoxin challenge

Peripheral injection of the endotoxin LPS in rats 3 weeks prior to a second injection of LPS derived from another bacterial strain results in elevated corticosterone and decreased pro-inflammatory cytokines in the blood. We further investigated this model by measuring cytokine expression in the hypothalamus and spleen. In LPS-pretreated rats, hypothalamic expression of a range of cytokines was attenuated in response to the second injection of LPS while splenic expression was elevated. This is the first demonstration that prior exposure to an endotoxin can differentially affect cytokine expression in the brain and peripheral tissues when a host is confronted with a second, acute, pro-inflammatory stimulus. Changes in hypothalamic cytokine expression in endotoxin pretreated rats may provide new evidence for the involvement of central cytokine pathways in modulating peripheral inflammation and mediating psychopathological alterations associated with inflammatory diseases.

Catecholamines can mediate stress-related effects on tumor progression

Studies have implicated behavior as a factor that can influence several aspects of health and have described the complex bidirectional interactions among the CNS, the endocrine system and the immune system that are involved. There is evidence that psychological factors can affect the incidence and progression of some cancers in humans. The hypothesis that stress could be a cofactor is supported by data obtained from animal models. Catecholamines, norepinephrine in particular, have been shown to directly affect various aspects of tumor development that is separate from the well-characterized effects on the cellular immune response to immunogenic tumors. Studies have shown that norepinephrine can directly affect tumor cell behavior and gene expression, further suggesting another mechanism for stress-related modulation of tumor progression. This line of research further suggests that interventions targeting components of the activated sympathetic-adrenal-medullary axis, or the utilization of β-adrenergic receptor-blocking agents, may represent new strategies for slowing down the progression of malignant disease and improving cancer patients' quality of life.

Central nervous system administration of interleukin-6 produces splenic sympathoexcitation

Interleukin-6 (IL-6) is a multifunctional cytokine that has been shown to play a pivotal role in centrally-mediated physiological responses including activation of the hypothalamic-pituitary-adrenal axis. Cerebral spinal fluid (CSF) concentrations of IL-6 are elevated in multiple pathophysiological conditions including Alzheimer's disease, autoimmune disease, and meningitis. Despite this, the effect of IL-6 on central regulation of sympathetic nerve discharge (SND) remains unknown which limits understanding of sympathetic-immune interactions in health and disease. In the present study we determined the effect of intracerebroventricular (i.c.v, lateral ventricle) administration of IL-6 on splenic SND in urethane-chloralose-anesthetized rats. A second goal was to determine if icv injected IL-6 enters the brain parenchyma and acts as a volume transmission signal to access areas of the brain involved in regulation of sympathetic nerve outflow. i.c.v administration of IL-6 (10 ng, 100 ng, and 400 ng) significantly and progressively increased splenic SND from control levels in baroreceptor-denervated Sprague-Dawley rats. Administration of 100-ng and 400-ng IL-6 resulted in significantly higher SND responses when compared to those elicited with a 10-ng dose. Sixty minutes following icv administration, fluorescently labeled IL-6 was not distributed throughout the parenchyma of the brain but was localized to the periventricular areas of the ventricular system. Brain sections counter-stained for the IL-6 receptor (IL-6R) revealed that IL-6 and the IL-6R were co-localized in periventricular areas adjoining the third ventricle. These results demonstrate that icv IL-6 administration increases splenic SND, an effect likely achieved via signaling mechanisms originating in the periventricular cells.

Catecholamines-crafty weapons in the inflammatory arsenal of immune/inflammatory cells or opening pandora's box?

It is well established that catecholamines (CAs), which regulate immune and inflammatory responses, derive from the adrenal medulla and from presynaptic neurons. Recent studies reveal that T cells also can synthesize and release catecholamines which then can regulate T cell function. We have shown recently that macrophages and neutrophils, when stimulated, can generate and release catecholamines de novo which, then, in an autocrine/paracrine manner, regulate mediator release from these phagocytes via engagement of adrenergic receptors. Moreover, regulation of catecholamine-generating enzymes as well as degrading enzymes clearly alter the inflammatory response of phagocytes, such as the release of proinflammatory mediators. Accordingly, it appears that phagocytic cells and lymphocytes may represent a major, newly recognized source of catecholamines that regulate inflammatory responses.

Effect of repeated restraint stress on the levels of intestinal IgA in mice

The effects of restraint stress on the intestinal humoral immune system, particularly those about intestinal IgA production, have not been explored in detail. Thus, the purpose of this study was to assess the effect of restraint stress on the production and secretion of intestinal IgA as well as on the number of IgA+ cells in the intestinal lamina propria. The involvement of glucocorticoids and catecholamines were also evaluated. Mice were exposed to 1 or 4 h restraint stress for 4 d. The intestinal IgA concentration was quantified by ELISA and the number of IgA containing cells in the lamina propria was determined by immunohistochemistry. The effects of restraint were also analyzed in mice submitted to different procedures: adrenalectomy, chemical sympathectomy, treatment with a glucocorticoid antagonist (RU486), dexamethasone and epinephrine. The main findings were that (1) chronic restraint-stress reduced the intestinal IgA concentration without changing the number of IgA+ cells in lamina propria; (2) adrenalectomy restored the production of IgA in stressed mice; (3) RU486 and chemical sympathectomy partially blocked the decrease in intestinal IgA in stressed mice; and (4) pharmacological doses of dexamethasone and epinephrine significantly reduced the intestinal IgA concentration and the number of IgA+ cells. The restraint stress probably reduced the intestinal IgA concentration through the effects of glucocorticoids and catecholamines.

Expression of alpha-AR subtypes in T lymphocytes and role of the alpha-ARs in mediating modulation of T cell function

OBJECTIVES

Previous work in our laboratory has shown that alpha-adrenoreceptors (alpha-ARs) and beta-ARs exist on lymphocytes from functional profile, and that the receptors mediate the regulation of lymphocyte function by catecholamines. In the present study, we directly examined the expression of alpha-AR subtypes, alpha(1)-AR and alpha(2)-AR mRNAs, in T lymphocytes and explored the roles of the alpha-AR subtypes and intracellular signal transduction mechanisms linked to the receptors in mediating the modulation of T lymphocyte function.

METHODS

T lymphocytes from mesenteric lymph nodes of rats were purified by using a nylon wool column. Reverse transcription polymerase chain reaction was used to detect the expression of alpha(1)-AR and alpha(2)-AR mRNAs in the freshly isolated T cells and the mitogen concanavalin A (Con A)-activated lymphocytes. Colorimetric methylthiazoletetrazolium assay was employed to measure lymphocyte proliferation induced by Con A. Interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) levels in the Con A-stimulated lymphocyte culture supernatants were examined by enzyme-linked immunosorbent assay.

RESULTS

T cells expressed both alpha(1)-AR and alpha(2)-AR mRNAs. The expression of both alpha(1)-AR and alpha(2)-AR mRNAs was significantly higher in the Con A-activated lymphocytes than in the resting lymphocytes. Phenylephrine, a selective alpha(1)-AR agonist, had no evident effect on lymphocyte proliferation nor on IFN-gamma and IL-4 production induced by Con A. However, the selective alpha(2)-AR agonist clonidine attenuated Con A-induced lymphocyte proliferation as well as IFN-gamma and IL-4 production. The inhibited lymphocyte proliferation and IFN-gamma and IL-4 production by clonidine were blocked by yohimbine, an alpha(2)-AR antagonist. Either phospholipase C inhibitor U-73122 or protein kinase C inhibitor chelerythrine partially prevented the suppressive effect of clonidine on Con A-stimulated lymphocyte proliferation and IL-4 production.

CONCLUSIONS

T lymphocytes express both alpha(1)-ARs and alpha(2)-ARs, but only the alpha(2)-ARs participate in the suppressive modulation of lymphocyte proliferation and cytokine production in vitro. The inhibitory effect of alpha(2)-AR stimulation on lymphocyte function is partially mediated via the phospholipase C-protein kinase C pathway.

Neuroendocrine System Response Modulates Oxidative Cellular Damage in Burn Patients

Oxygen-derived free radicals play important roles in pathophysiological processes in critically ill patients, but the data characterizing relationships between radicals and neuroendocrine system response are sparse. To search the cue to reduce the oxidative cellular damage from the point of view of neuroendocrine system response, we studied the indicators of neuroendocrine and inflammatory responses excreted in urine in 14 burn patients (42.3 +/- 31.4 years old, and 32.3 +/- 27.6% burn of total body surface area [%TBSA]) during the first seven days post burn. The daily mean amounts of urinary excretion of 8-hydroxy-2'-deoxy-guanosine (8-OHdG), a marker of oxidative cellular damage, were above the upper limit of the standard value during the studied period. The total amount of urinary excretion of 8-OHdG in the first day post burn correlated with burn severity indices: %TBSA (r = 0.63, p = 0.021) and burn index (r = 0.70, p = 0.008). The daily urinary excretion of 8-OHdG correlated with the daily urinary excretion of norepinephrine and nitrite plus nitrate (NOx) during the studied period except day 2 post burn, and correlated with the daily urinary excretion of 17-hydroxycorticosteriod (17-OHCS) in days 2, 3, and 7 post burn. These data suggest that oxidative cellular damage correlates with burn severity and neuroendocrine system response modulates inflammation and oxidative cellular damage. Modulation of neuroendocrine system response and inflammation in the treatment in the early phase of burn may be useful to reduce the oxidative cellular damage and to prevent multiple organ failures in patients with extensive burn.

Hematologic abnormalities within the first week after acute isolated traumatic cervical spinal cord injury: a case-control cohort study

STUDY DESIGN

Case-control cohort study.

OBJECTIVE

To evaluate 1) the hematologic abnormalities within the first week following isolated acute cervical spine trauma or spinal cord injury (SCI); and 2) the influence of age, sex, and severity of SCI on these hematologic abnormalities.

SUMMARY OF BACKGROUND DATA

Given that autonomic nervous system has a critical role in the regulation of the hematopoietic system, we sought to evaluate the potential association between hematologic abnormalities within the first week posttrauma and the severity of SCI.

METHODS

All consecutive individuals with isolated acute cervical spine trauma admitted to our institution from 1998 to 2000 were reviewed. Exclusion criteria included preexisting medical comorbidities and polytrauma. The study population was divided into a SCI group and a control group (individuals with spine trauma without neurologic impairment). The SCI group was subdivided into patients with motor complete SCI (American Spinal Injury Association [ASIA] Grades A/B) and individuals with motor incomplete SCI (ASIA Grades C/D).

RESULTS

There were 21 SCI individuals (15 male, 6 female; ages 17-83 years; mean, 57 years) and 11 controls (6 male, 5 female; ages 18-75 years; mean, 41 years). When controlled for age, SCI individuals showed a significantly higher frequency of reduced hemoglobin concentration (RHC), leukocytosis, lymphopenia, and thrombocytopenia than controls within the first week posttrauma. Blood hemoglobin concentration, lymphocyte, and platelet counts in the SCI group were significant lower than the controls. The SCI group showed a significant higher leukocyte count than the controls. The degree of RHC and lymphopenia was significantly correlated with the severity of SCI.

CONCLUSION

Our results indicate that patients with isolated cervical SCI have significantly greater frequency of RHC, leukocytosis, lymphopenia, and thrombocytopenia than controls during the first week posttrauma. The degree of RHC and lymphopenia was significantly associated with the severity of SCI. While the mechanisms underlying these clinically important hematologic consequences of SCI remain undetermined, evidence from the literature suggests that acute autonomic denervation of the hematopoietic system could play a key role.

Protective effects of endotoxin in a rat model of chronic inflammation are accompanied by suppressed secretion of pro-inflammatory cytokines and biphasic alteration in hypothalamo-pituitary-adrenal axis activity

We have previously demonstrated that Gram-negative bacterial endotoxin can exert long-term protective effects against the chronic inflammatory disease adjuvant arthritis in rats. The present study was designed to investigate the mechanisms and time-course of hypothalamo-pituitary-adrenocortical (HPA) axis activity and cytokine secretion underlying this phenomenon. Rats were injected with endotoxin (lipopolysaccharide) and blood was collected either 7 or 21 days later. Priming with endotoxin induced a biphasic alteration in secretion of adrenocorticotrophic hormone and corticosterone in response to a second injection of endotoxin, with decreased secretion observed after 7 days whereas robust secretion was observed at 21 days. Seven days following priming with endotoxin, plasma concentrations of pro-inflammatory cytokines interleukin (IL)-6 and interferon (IFN)-gamma were reduced by 90%, and tumour necrosis factor (TNF)-alpha by 70%, compared to saline-treated rats, whereas robust secretion of the anti-inflammatory cytokine IL-10 was maintained in both groups. A similar net change favouring an anti-inflammatory cytokine secretory milieu was also observed 21 days following priming with endotoxin. This study provides evidence that the long-term protective effects of endotoxin on inflammation are associated with a sustained reduction in secretion of pro-inflammatory cytokines. HPA axis hypoactivity at 7 days suggests that corticosterone is not involved in suppressing IL-6, IFN-gamma and TNF-alpha at this time point. Conversely, hypersecretion of corticosterone at 21 days may underlie synchronous suppression of IL-6 and IFN-gamma. These data provide novel insight into interactions between HPA axis activity and cytokine secretion following endotoxin priming prior to induction of inflammatory disease.

AN INTRODUCED GENERALIST PARASITE, THE STICKTIGHT FLEA (ECHIDNOPHAGA GALLINACEA), AND ITS PATHOLOGY IN THE THREATENED FLORIDA SCRUB-JAY (APHELOCOMA COERULESCENS)

The sticktight flea, (Echidnophaga gallinacea), a major pest of the domestic chicken (Gallus gallus) that can cause severe pathology or death if untreated, is rarely recorded in free-living avian species. Sticktight fleas, however, were observed on the federally threatened Florida scrub-jay (Aphelocoma coerulescens) in February 2004, in south central Florida. Of the 81 Florida scrub-jays (FSJs) sampled before the 2004 breeding season, 12 were infested, with from 1 to as many as 57 fleas. Subsequent survivorship and variation in health indices led us to conclude that the sticktight flea caused the death of several jays. Within 4 mo, 46% of sticktight flea-infested (INF) jays died, whereas in the nonflea-infested (NINF) jays, only 5.9% died. Adult INF birds lost body mass in the time since a previous capture compared with NINF jays, and mass gain was slowed in 1-yr-old INF jays. Hematocrit of INF jays was dramatically impacted, as low as 17%, and was negatively correlated with the extent of infestation. Leukocyte counts were highest in INF jays; however, plasma immunoglobulin levels were lowest. Physiological stress levels, measured using plasma corticosterone, increased more rapidly in INF jays than NINF jays and were positively correlated with heterophil/lymphocyte ratios. The impact of the sticktight flea on the federally threatened FSJ negates previous findings that sticktight fleas are benign in wild avian hosts.

Endocrine stress responses in TH1-mediated chronic inflammatory skin disease (psoriasis vulgaris)--do they parallel stress-induced endocrine changes in TH2-mediated inflammatory dermatoses (atopic dermatitis)?

In previous research we reported attenuated responsiveness of the hypothalamus-pituitary-adrenal (HPA) axis and further, an increased reactivity of the sympathetic adrenomedullary (SAM) system to stress in patients suffering from atopic dermatitis (AD). AD is a chronic inflammatory skin disease mainly triggered by TH(2)-dependent inflammatory processes. The specific goal of the present study was to investigate whether altered HPA axis and SAM system responsiveness to stress can also be found in TH(1)-mediated inflammatory conditions. Patients with psoriasis (PSO; n=23), a TH(1)-mediated inflammatory (autoimmune) skin disease and healthy controls (n=25) were exposed to a standardized laboratory stressor (TSST) which mainly consists of a free speech and a mental arithmetic task in front of an audience. To investigate HPA axis and SAM system responsiveness, cortisol, ACTH, and catecholamines were determined before and after the stress test. In addition, cortisol levels after awakening and cortisol levels during the day (short diurnal profile) were determined. In order to test feedback sensitivity of the HPA axis, a dexamethasone (DEX) suppression test (0.5 mg) was performed. Analysis of cortisol and ACTH levels after the stress test yielded no significant differences between PSO subjects and controls indicating no altered HPA axis function in this patient group. Further, no between-group differences were found in cortisol levels after awakening or during the day (short diurnal profile). Additionally, no difference between PSO and healthy subjects in the feedback sensitivity of the system could be found (DEX test). However, PSO patients showed elevated epinephrine (F(3,102)=4.7; p<0.005) and norepinephrine (F(3,135)=2.7; p<0.05) levels in response to the stress test when compared to the controls. These findings suggest no altered HPA axis responsiveness, but increased reactivity of the SAM system in TH(1)-mediated chronic inflammatory skin disease.

Effect of endogenous catecholamines in lymphocytes on lymphocyte function

Our previous work has showed that lymphocytes can synthesize catecholamines (CAs). However, role and mechanism of the endogenous CAs in lymphocytes in modulation of immune function are less known. In the present study, we used alpha-methyl-p-tyrosine (alpha-MT), an inhibitor of tyrosine hydroxylase (TH), and pargyline, an inhibitor of monoamine oxydase, to block the synthesis and degradation of CAs in lymphocytes and then observed changes of lymphocyte proliferation induced by concanavalin A (Con A). Phentolamine and propranolol, antagonists respectively to alpha- and beta-adrenoreceptors, were employed to investigate the receptor mechanism. We found that TH mRNA in the Con A-activated lymphocytes was 2.4 times higher in relative density than that in the resting lymphocytes. Similarly, the intracellular and supernatant CAs, including DA, NE and E, of the Con A-stimulated lymphocytes were significantly raised relative to those of the resting cells. alpha-MT (10(-11), 10(-10) and 10(-9) M) facilitated the Con A-induced lymphocyte proliferation, but pargyline (10(-11), 10(-10) and 10(-9) M) attenuated the cell proliferation. Meanwhile, alpha-MT and pargyline respectively led to decrease and increase in the intracellular and supernatant CAs (DA, NE and E) of the Con A-stimulated lymphocytes. Propranolol completely blocked, but phentolamine partly reversed, the suppressive effect of pargyline on the Con A-induced lymphocyte proliferation. Content of cAMP was remarkably increased in the lymphocytes treated with pargyline alone, but it dropped to control level after these cells were treated with propranolol plus pargyline. These results on the one hand further demonstrate the ability of lymphocytes to synthesize CAs and the enhancive ability of the activated lymphocytes to synthesize CAs, and on the other hand reveal an important role of the endogenous CAs in regulation of function of lymphocytes themselves. Besides, our present findings suggest that CAs synthesized by lymphocytes can secrete out of the lymphocytes via paracrine or autocrine pathway and affect lymphocyte function by beta-adrenoreceptor and cAMP mediating mechanism. Thus, it can be implied that CAs in lymphocytes are also involved in the cross-talk in the neuro-endocrine-immune networks.

Physical Activity and Stress Resistance: Sympathetic Nervous System Adaptations Prevent Stress-Induced Immunosuppression

A physically active lifestyle incurs many health benefits. One recently recognized benefit of regular moderate exercise is stress reduction. The current review develops the hypothesis that physical activity may prevent stress-induced suppression of the immune system and suggests an immunophysiological mechanism (sympathetic nervous system constraint) for this effect.

Effect of lesions of cerebellar fastigial nuclei on lymphocyte functions of rats

The cerebellum, probably owing to its traditional concept limited to motor control, is less well studied in immunoregulation. To obtain more comprehension and knowledge on cerebellar functions, we investigated effect of cerebellar fastigial nucleus (FN), an output nucleus of the spinocerebellum, on lymphocyte functions, and explored central and peripheral pathways involved in the effect. Kainic acid (KA) was microinjected into bilateral FN of rats (0.4 microg KA in 0.4 microl saline for each side) to destroy neurons of the nuclei. On days 8, 16 and 32 following the FN lesions, methyl-thiazole-tetrazolium (MTT) assay and flow cytometry were used to measure proliferation of concanavalin A (Con A)-induced lymphocytes and cytotoxicity of natural killer (NK) cells against YAC-1 cells, respectively. Meanwhile, glutamate and monoamine neurotransmitters, including norepinephrine (NE), dopamine (DA) and 5-hydroxytryptamine (5-HT), in the hypothalamus and the spleen were determined by means of high-performance liquid chromatography (HPLC) assay. Adrenocorticotropic hormone (ACTH) and cortisol in the plasma were also detected respectively by radioimmunoassay and chemiluminescent immunoassay after the FN lesions. We found that the Con A-induced lymphocyte proliferation and the NK cell cytotoxicity were both significantly enhanced on days 8, 16 and 32 following the effective lesions of the bilateral FN in comparison with those of matching control rats microinjected with saline in their FN. Contents of glutamate and NE, not DA and 5-HT, in the hypothalamus, and concentration of NE, not DA, in the spleen were all remarkably reduced on the 16th day following the FN lesions, when both the T lymphocyte proliferation and the NK cell cytotoxicity were dramatically increased. However, levels of ACTH and cortisol in the plasma had no notable differences between FN lesion rats and FN saline ones when the enhanced T and NK cell functions occurred. These findings reveal that the cerebellar FN participates in the modulation of lymphocyte functions and that the hypothalamus and sympathetic nerves innervating lymphoid organs are involved in this neuroimmunomodulation. Thus, a possible central and peripheral pathway for the spinocerebellum to regulate lymphocyte functions is suggested, i.e. cerebellum-hypothalamus-sympathetic nerves-lymphocytes, while the functional axis of hypothalamus-pituitary-adrenal gland may not contribute to mediation of the spinocerebellar immunomodulation.

Effects of stress on inflammatory autoimmune disease: destructive or protective?

We have summarised evidence in the literature for modulatory effects of stress on inflammatory autoimmune disease. We find that overall there is strong evidence for such an interrelationship. Apparent discrepancies between groups and studies are probably due to differences in experimental design, whether longitudinal or retrospective. Other important variables are the specific effects of different types of stress and the intensity and timing of the stressor relative to onset of inflammation. We conclude that there is much of benefit to be learned from scientific study of stress, such as harnessing and rationalising of stressful experiences through self-expression in patients, or the identification of novel anti-inflammatory compounds activated by stress.

The importance of timing of adrenergic drug delivery in relation to the induction and onset of adjuvant-induced arthritis

Stressful events often precede onset and exacerbate established rheumatic diseases. There are numerous reports of abnormal autonomic function in rheumatoid arthritis (RA) patients. Targeting the sympathetic nervous system (SNS) with adrenergic receptor (AR) drugs in RA patients and animal models of the disease have revealed mixed results, with treatments inhibiting and exacerbating disease pathology. We tested the hypothesis that variability in disease outcome following adrenergic drug treatment is due to different roles played by the SNS at different disease stages. The contribution of beta2- and alpha-AR subtypes to disease pathology was studied at different disease stages in adjuvant-induced arthritis (AA), an animal model of RA. Lewis rats were given twice-daily intraperitoneal (i.p.) injections of an alpha-AR antagonist (phentolamine: 500 microg/kg) or a beta2-AR agonist (terbutaline: 1200 microg/day), initiated at adjuvant challenge or disease onset, and continued through severe disease. Both adrenergic therapies, when initiated at adjuvant challenge exacerbated disease pathology. In contrast, SH1293, an adrenergic drug that targets both alpha- and beta-AR (300 microg/day; twice-daily), initiated at adjuvant challenge did not exacerbate disease severity. Additionally, the same treatment regimen of phentolamine, terbutaline or SH1293 initiated at disease onset attenuated joint-inflammation and dramatically reduced bone destruction in the arthritic hind limbs. These data support the SNS playing different roles in disease pathology preclinically and after disease onset. Given current drug therapies are not effective in preventing bone destruction, these data support using adrenergic drugs as bone sparing treatments in RA.

Photoperiod modulates the effects of norepinephrine on lymphocyte proliferation in Siberian hamsters

Siberian hamsters (Phodopus sungorus) rely on photoperiod to coordinate seasonally appropriate changes in physiology, including immune function. Immunity is regulated, in part, by the sympathetic nervous system (SNS), although the precise role of the SNS in regulating photoperiodic changes in immunity remains unspecified. The goal of the present study was to examine the contributions of norepinephrine (NE), the predominant neurotransmitter of the SNS, to photoperiodic changes in lymphocyte proliferation. In experiment 1, animals were maintained in long [16:8-h light-dark cycle (16:8 LD)] or short days (8:16 LD) for 10 wk, and splenic NE content was determined. In experiment 2, in vitro splenocyte proliferation in response to mitogenic stimulation (concanavalin A) was assessed in spleen cell suspensions taken from long- or short-day hamsters in which varying concentrations of NE were added to the cultures. In experiment 3, splenocyte proliferation was examined in the presence of NE and selective alpha- and beta-noradrenergic receptor antagonists (phenoxybenzamine and propranolol, respectively) in vitro. Short-day animals had increased splenic NE content compared with long-day animals. Long-day animals had higher proliferation compared with short-day animals independent of NE. NE (1 microM) further suppressed splenocyte proliferation in short but not long days. Last, NE-induced suppression of proliferation in short-day hamsters was blocked by propranolol but not phenoxybenzamine. The present results suggest that NE plays a role in photoperiodic changes in lymphocyte proliferation. Additionally, the data suggest that the effects of NE on proliferation are specific to activation of beta-adrenergic receptors located on splenic tissue. Collectively, these results provide further support that photoperiodic changes in immunity are influenced by changes in SNS activity.