An overview of the role of sympathetic regulation of immune responses in infectious disease and autoimmunity

The concomitant use of ultra short beta-blockers with vasopressors and inotropes in critically ill patients with septic shock: A systematic review and meta-analysis of randomized controlled trials

Background

Septic shock is associated with systemic inflammatory response, hemodynamic instability, impaired sympathetic control, and the development of multiorgan dysfunction that requires vasopressor or inotropic support. The regulation of immune function in sepsis is complex and varies over time. However, activating Beta-2 receptors and blocking Beta-1 receptors reduces the proinflammatory response by influencing cytokine production. Evidence that supports the concomitant use of ultra short beta-blockers with inotropes and vasopressors in patients with septic shock is still limited. This study aimed to evaluate the use of ultra short beta-blockers and its impact on the ICU related outcomes such as mortality, length of stay, heart rate control, shock resolution, and vasopressors/inotropes requirements.

Methods

A systematic review and meta-analysis of randomized controlled trials including critically ill patients with septic shock who received inotropes and vasopressors. Patients who received either epinephrine or norepinephrine without beta-blockers "control group" were compared to patients who received ultra short beta-blockers concomitantly with either epinephrine or norepinephrine "Intervention group". MEDLINE and Embase databases were utilized to systematically search for studies investigating the use of ultra short beta-blockers in critically ill patients on either epinephrine or norepinephrine from inception to October 10, 2023. The primary outcome was the 28-day mortality. While, length of stay, heart rate control, and inotropes/ vasopressors requirements were considered secondary outcomes.

Results

Among 47 potentially relevant studies, nine were included in the analysis. The 28-day mortality risk was lower in patients with septic shock who used ultra short beta-blockers concomitantly with either epinephrine or norepinephrine compared with the control group (RR (95%CI): 0.69 (0.53, 0.89), I2=26%; P=0.24). In addition, heart rate was statistically significantly lower with a standardized mean difference (SMD) of -22.39 (95% CI: -24.71, -20.06) among the beta-blockers group than the control group. The SMD for hospital length of stay and the inotropes requirement were not statistically different between the two groups (SMD (95%CI): -0.57 (-2.77, 1.64), and SMD (95%CI): 0.08 (-0.02, 0.19), respectively).

Conclusion

The use of ultra short beta-blockers concomitantly with either epinephrine or norepinephrine in critically ill patients with septic shock was associated with better heart rate control and survival benefits without increment in the inotropes and vasopressors requirement.

Pathological mechanisms of cold and mechanical stress in modulating cancer progression

Environmental temperature and cellular mechanical force are the inherent factors that participate in various biological processes and regulate cancer progress, which have been hot topics worldwide. They occupy a dominant part in the cancer tissues through different approaches. However, extensive investigation regarding pathological mechanisms in the carcinogenic field. After research, we found cold stress via two means to manipulate tumors: neuroscience and mechanically sensitive ion channels (MICHs) such as TRP families to regulate the physiological and pathological activities. Excessive cold stimulation mediated neuroscience acting on every cancer stage through the hypothalamus-pituitary-adrenocorticoid (HPA) to reach the target organs. Comparatively speaking, mechanical force via Piezo of MICHs controls cancer development. The progression of cancer depends on the internal activation of proto-oncogenes and the external tumorigenic factors; the above two means eventually lead to genetic disorders at the molecular level. This review summarizes the interaction of bidirectional communication between them and the tumor. It covers the main processes from cytoplasm to nucleus related to metastasis cascade and tumor immune escape.

T cells at the interface of neuroimmune communication

The immune system protects the host from infection and works to heal damaged tissue after infection or injury. There is increasing evidence that the immune system and the nervous system work in concert to achieve these goals. The sensory nervous system senses injury, infection, and inflammation, which results in a direct pain signal. Direct activation of peripheral sensory nerves can drive an inflammatory response in the skin. Immune cells express receptors for numerous transmitters released from sensory and autonomic nerves, which allows the nervous system to communicate directly with the immune system. This communication is bidirectional because immune cells can also produce neurotransmitters. Both innate and adaptive immune cells respond to neuronal signaling, but T cells appear to be at the helm of neuroimmune communication.

Inflammatory biomarkers link perceived stress with metabolic dysregulation

Objective

Perceived stress has been identified as a risk factor for metabolic syndrome. However, the intermediate pathways underlying this relationship are not well understood. Inflammatory responses may be one process by which stress leads to metabolic dysregulation. Prior work has shown that chronic stress is associated with elevated systemic inflammation and that altered inflammatory activity contributes to the pathogenesis of metabolic syndrome. The current analyses tested this hypothesis by examining inflammation as a pathway by which perceived stress affects metabolic health.

Methods

Data from the Midlife in the United States Study (MIDUS) (N = 648; Mean age = 52.3) provided measures of perceived stress, inflammatory biomarkers [C-reactive protein (CRP), interleukin-6 (IL-6), E-selectin, fibrinogen, intracellular adhesion molecule-1 (ICAM-1)] and metabolic health markers. Confirmatory factor analysis (CFA) was used to confirm the fit of a hierarchical model of metabolic syndrome in our sample. Structural equation modeling (SEM) was used to test the assumption that inflammation mediates the association between perceived stress and the latent factor representing metabolic syndrome.

Results

The CFA of metabolic syndrome demonstrated excellent goodness of fit to our sample [CFI = 0.97, TLI = 0.95, RMSEA = 0.06, SMSR = 0.05]. Mediation analysis with SEM revealed that the indirect pathway linking stress to metabolic dysregulation through inflammation was significant [B = 0.08, SE = 0.01, z = 3.69, p < .001, 95% confidence interval CI (0.04, 0.13)].

Conclusions

These results suggest that inflammatory biomarkers are a viable explanatory pathway for the relationship between perceived stress and metabolic health consequences. Interventions that target psychosocial stress may serve as cost-effective and accessible treatment options for mitigating inflammatory health risks.

Influence of Housing Temperature and Genetic Diversity on Allogeneic T Cell-Induced Tissue Damage in Mice

The objective of this study was to determine how housing temperature and genetic diversity affect the onset and severity of allogeneic T cell-induced tissue damage in mice subjected to reduced intensity conditioning (RIC). We found that adoptive transfer of allogeneic CD4+ T cells from inbred donors into sub-lethally irradiated inbred recipients (I→I) housed at standard housing temperatures (ST; 22-24 °C) induced extensive BM and spleen damage in the absence of injury to any other tissue. Although engraftment of T cells in RIC-treated mice housed at their thermo-neutral temperature (TNT; 30-32 °C) also developed similar BM and spleen damage, their survival was markedly and significantly increased when compared to their ST counterparts. In contrast, the adoptive transfer of allogeneic T cells into RIC-treated outbred CD1 recipients failed to induce disease in any tissue at ST or TNT. The lack of tissue damage was not due to defects in donor T cell trafficking to BM or spleen but was associated with the presence of large numbers of B cells and myeloid cells within these tissues that are known to contain immunosuppressive regulatory B cells and myeloid-derived suppressor cells. These data demonstrate, for the first time, that housing temperature affects the survival of RIC-treated I→I mice and that RIC-conditioned outbred mice are resistant to allogeneic T cell-induced BM and spleen damage.

Measuring neuron-regulated immune cell physiology via the alpha-2 adrenergic receptor in an ex vivo murine spleen model

The communication between the nervous and immune systems plays a crucial role in regulating immune cell function and inflammatory responses. Sympathetic neurons, which innervate the spleen, have been implicated in modulating immune cell activity. The neurotransmitter norepinephrine (NE), released by sympathetic neurons, influences immune cell responses by binding to adrenergic receptors on their surface. The alpha-2 adrenergic receptor (α2AR), expressed predominantly on sympathetic neurons, has received attention due to its autoreceptor function and ability to modulate NE release. In this study, we used fast-scan cyclic voltammetry (FSCV) to provide the first subsecond measurements of NE released in the white pulp region of the spleen and validated it with yohimbine, a known antagonist of α2AR. For further application of FSCV in neuroimmunology, we investigated the extent to which subsecond NE from sympathetic neurons is important for immune cell physiology and cytokine production, focusing on tumor necrosis factor-alpha (TNF-α), interleukin-10 (IL-10), and interleukin-6 (IL-6). Our findings provide insights into the regulatory mechanisms underlying sympathetic-immune interactions and show the significance of using FSCV, a traditional neurochemistry technique, to study these neuroimmune mechanisms.

Acute repeated cage exchange stress modifies urinary stress and plasma metabolic profiles in male mice

Exposure to a novel environment is psychologically and physically stressful for humans and animals. The response has been reported to involve enhanced sympathetic nervous system activity, but changes in nutrient levels under stress are not fully understood. As a form of exposure to a novel environment, repeated cage exchange (CE, four times at 2-h intervals for 8 h from 08:00 h) during the light phase with no restraint on movement was applied to A/J mice, a strain particularly prone to stress. Body temperature was measured with a temperature-sensing microchip implanted in the interscapular region. The stress conditions and anxiety level were evaluated by measuring urinary catecholamines and corticosterone and by performing an anxiety-like behavior test, respectively. Major nutrients such as glucose, fatty acids, and amino acids in the plasma were also examined. CE mice showed a significant increase in body temperature with each CE. They also showed a significantly greater reduction of body weight change, more water intake, and higher levels of urinary catecholamines and corticosterone and anxiety-like behavior score than control mice. The model revealed a significantly lower plasma glucose level and higher levels of several essential amino acids, such as branched-chain amino acids and phenylalanine, than those of control mice. Meanwhile, free fatty acids and several amino acids such as arginine, aspartic acid, proline, threonine, and tryptophan in both sets of mice were significantly decreased from the corresponding levels at 08:00 h, while similar plasma levels were exhibited between mice with and without CE. In conclusion, repeated CE stress was associated with changes in glucose and amino acids in plasma. Although further study is needed to clarify how these changes are specifically linked to anxiety-like behavior, this study suggests the potential for nutritional intervention to counter stress in humans exposed to novel environments.

Menstrual disturbances following COVID-19 vaccination: A probable puzzle about the role of endocrine and immune pathways

Menstruation is a monthly shedding of the uterine wall, presented by menstrual bleeding in women of reproductive age. Menstruation is regulated by fluctuation of estrogen and progesterone, as well as other endocrine and immune pathways. Many women experienced menstrual disturbances after vaccination against the novel coronavirus in the last two years. Vaccine-induced menstrual disturbances have led to discomfort and concern among reproductive-age women, such that some decided not to receive the subsequent doses of the vaccine. Although many vaccinated women report these menstrual disturbances, the mechanism is still poorly understood. This review article discusses the endocrine and immune changes following COVID-19 vaccination and the possible mechanisms of vaccine-related menstrual disturbances.

Chronic adrenergic stress and generation of myeloid-derived suppressor cells: Implications for cancer immunotherapy in dogs

Recent studies have highlighted a key role played by the sympathetic nervous system (SNS) and adrenergic stress in mediating immune suppression associated with chronic inflammation in cancer and other diseases. The connection between chronic SNS activation, adrenergic stress and immune suppression is linked in part to the ability of catecholamines to stimulate the bone marrow release and differentiation of myeloid-derived suppressor cells (MDSC). Rodent model studies have revealed an important role for β-adrenergic receptor signalling in suppression of cancer immunity in mice subjected to chronic stresses, including thermal stress. Importantly, therapeutic blockade of beta-adrenergic responses by drugs such as propranolol can partially reverse the generation and differentiation of MDSC, and partly restore tumour immunity. Clinical trials in both humans and dogs with cancer have demonstrated that propranolol blockade can improve responses to radiation therapy, cancer vaccines and immune checkpoint inhibitors. Thus, the SNS stress response has become an important new target to relieve immune suppression in cancer and other chronic inflammatory conditions.

Adrenergic receptor signaling regulates the CD40-receptor mediated anti-tumor immunity

Inroduction

Anti-CD40 agonistic antibody (αCD40), an activator of dendritic cells (DC) can enhance antigen presentation and activate cytotoxic T-cells against poorly immunogenic tumors. However, cancer immunotherapy trials also suggest that αCD40 is only moderately effective in patients, falling short of achieving clinical success. Identifying factors that decrease αCD40 immune-stimulating effects can aid the translation of this agent to clinical reality.

Method/Results

Here, we reveal that β-adrenergic signaling on DCs directly interferes with αCD40 efficacy in immunologically cold head and neck tumor model. We discovered that β-2 adrenergic receptor (β2AR) activation rewires CD40 signaling in DCs by directly inhibiting the phosphorylation of IκBα and indirectly by upregulating levels of phosphorylated-cAMP response element-binding protein (pCREB). Importantly, the addition of propranolol, a pan β-Blocker reprograms the CD40 pathways, inducing superior tumor regressions, increased infiltration of cytotoxic T-cells, and a reduced burden of regulatory T-cells in tumors compared to monotherapy.

Discussion/Conclusion

Thus, our study highlights an important mechanistic link between stress-induced β2AR signaling and reduced αCD40 efficacy in cold tumors, providing a new combinatorial approach to improve clinical outcomes in patients.

The link between immunity and hypertension in the kidney and heart

Hypertension is the primary cause of cardiovascular disease, which is a leading killer worldwide. Despite the prevalence of this non-communicable disease, still between 90% and 95% of cases are of unknown or multivariate cause ("essential hypertension"). Current therapeutic options focus primarily on lowering blood pressure through decreasing peripheral resistance or reducing fluid volume, but fewer than half of hypertensive patients can reach blood pressure control. Hence, identifying unknown mechanisms causing essential hypertension and designing new treatment accordingly are critically needed for improving public health. In recent years, the immune system has been increasingly implicated in contributing to a plethora of cardiovascular diseases. Many studies have demonstrated the critical role of the immune system in the pathogenesis of hypertension, particularly through pro-inflammatory mechanisms within the kidney and heart, which, eventually, drive a myriad of renal and cardiovascular diseases. However, the precise mechanisms and potential therapeutic targets remain largely unknown. Therefore, identifying which immune players are contributing to local inflammation and characterizing pro-inflammatory molecules and mechanisms involved will provide promising new therapeutic targets that could lower blood pressure and prevent progression from hypertension into renal or cardiac dysfunction.

Kinetics of Plasma Cell-Free DNA under a Highly Standardized and Controlled Stress Induction

Psychological stress affects the immune system and activates peripheral inflammatory pathways. Circulating cell-free DNA (cfDNA) is associated with systemic inflammation, and recent research indicates that cfDNA is an inflammatory marker that is sensitive to psychological stress in humans. The present study investigated the effects of acute stress on the kinetics of cfDNA in a within-subjects design. Twenty-nine males (mean age: 24.34 ± 4.08 years) underwent both the Trier Social Stress Test (TSST) and a resting condition. Blood samples were collected at two time points before and at 9 time points up to 105 min after both conditions. The cfDNA immediately increased 2-fold after the TSST and returned to baseline levels after 30 min after the test, showing that a brief psychological stressor was sufficient to evoke a robust and rapid increase in cfDNA levels. No associations were detected between perceived stress, whereas subjects with higher basal cfDNA levels showed higher increases. The rapid cfDNA regulation might be attributed to the transient activation of immune cells caused by neuroendocrine-immune activation. Further research is required to evaluate the reliability of cfDNA as a marker of neuroendocrine-immune activation, which could be used for diagnostics purposes or monitoring of treatment progression.

Stress, mindfulness, and systemic lupus erythematosus: An overview and directions for future research

Although the pathogenesis of autoimmunity is not fully understood, it is thought to involve genetic, hormonal, immunologic, and environmental factors. Stress has been evaluated as a potential trigger for autoimmunity and disease flares in patients with systemic lupus erythematosus (SLE). The physiologic changes that occur with stress involve numerous catecholamines, hormones, and cytokines that communicate intricately with the immune system. There is some evidence that these systems may be dysregulated in patients with autoimmune disease. Mindfulness-based techniques are practices aimed at mitigating stress response and have been shown to improve quality of life in general population. This review will discuss pathophysiology of chronic stress as it relates to SLE, evidence behind mindfulness-based practices in these patients, and directions for future research.

The Role of β-Adrenergic Receptors in the Regulation of the Functions of Innate Immune Cells during Cold Stress In Vivo

It was found that 10-min cold stress enhanced stimulated production of ROS, while 60-min cold stress increased both spontaneous and stimulated ROS production by peritoneal macrophages. β-Adrenergic receptor blockade leveled the effect of 10-min stress in stimulated cultures and the effect of 60-min stress in spontaneous cultures. None variants of cold stress affected spontaneous and stimulated production of IL-1β. We observed an increase in the production of IL-1β in stimulated cultures from animals subjected to 10- and 60-min stress against the background of propranolol. At the same time, both variants of cold exposure, irrespective of β-adrenergic receptor blockade, stimulated IL-10 synthesis in spontaneous and activated samples. None of the used models of cold exposure affected the phagocytic activity of peritoneal macrophages. Thus, β-adrenergic receptors are directly involved in the regulation of cytokine production and microbicidal potential of macrophages in acute cold stress.

Sympathetic Nerves and Innate Immune System in the Spleen: Implications of Impairment in HIV-1 and Relevant Models

The immune and sympathetic nervous systems are major targets of human, murine and simian immunodeficiency viruses (HIV-1, MAIDS, and SIV, respectively). The spleen is a major reservoir for these retroviruses, providing a sanctuary for persistent infection of myeloid cells in the white and red pulps. This is despite the fact that circulating HIV-1 levels remain undetectable in infected patients receiving combined antiretroviral therapy. These viruses sequester in immune organs, preventing effective cures. The spleen remains understudied in its role in HIV-1 pathogenesis, despite it hosting a quarter of the body’s lymphocytes and diverse macrophage populations targeted by HIV-1. HIV-1 infection reduces the white pulp, and induces perivascular hyalinization, vascular dysfunction, tissue infarction, and chronic inflammation characterized by activated epithelial-like macrophages. LP-BM5, the retrovirus that induces MAIDS, is a well-established model of AIDS. Immune pathology in MAIDs is similar to SIV and HIV-1 infection. As in SIV and HIV, MAIDS markedly changes splenic architecture, and causes sympathetic dysfunction, contributing to inflammation and immune dysfunction. In MAIDs, SIV, and HIV, the viruses commandeer splenic macrophages for their replication, and shift macrophages to an M2 phenotype. Additionally, in plasmacytoid dendritic cells, HIV-1 blocks sympathetic augmentation of interferon-β (IFN-β) transcription, which promotes viral replication. Here, we review viral–sympathetic interactions in innate immunity and pathophysiology in the spleen in HIV-1 and relevant models. The situation remains that research in this area is still sparse and original hypotheses proposed largely remain unanswered.

Adrenergic and Glucocorticoid Receptors in the Pulmonary Health Effects of Air Pollution

Adrenergic receptors (ARs) and glucocorticoid receptors (GRs) are activated by circulating catecholamines and glucocorticoids, respectively. These receptors regulate the homeostasis of physiological processes with specificity via multiple receptor subtypes, wide tissue-specific distribution, and interactions with other receptors and signaling processes. Based on their physiological roles, ARs and GRs are widely manipulated therapeutically for chronic diseases. Although these receptors play key roles in inflammatory and cellular homeostatic processes, little research has addressed their involvement in the health effects of air pollution. We have recently demonstrated that ozone, a prototypic air pollutant, mediates pulmonary and systemic effects through the activation of these receptors. A single exposure to ozone induces the sympathetic–adrenal–medullary and hypothalamic–pituitary–adrenal axes, resulting in the release of epinephrine and corticosterone into the circulation. These hormones act as ligands for ARs and GRs. The roles of beta AR (βARs) and GRs in ozone-induced pulmonary injury and inflammation were confirmed in a number of studies using interventional approaches. Accordingly, the activation status of ARs and GRs is critical in mediating the health effects of inhaled irritants. In this paper, we review the cellular distribution and functions of ARs and GRs, their lung-specific localization, and their involvement in ozone-induced health effects, in order to capture attention for future research.

Crosstalk Between Epithelial Cells, Neurons and Immune Mediators in HSV-1 Skin Infection

Herpes simplex virus type 1 (HSV-1) infection is highly prevalent in humans, with approximately two-thirds of the world population living with this virus. However, only a fraction of those carrying HSV-1, which elicits lifelong infections, are symptomatic. HSV-1 mainly causes lesions in the skin and mucosae but reaches the termini of sensory neurons innervating these tissues and travels in a retrograde manner to the neuron cell body where it establishes persistent infection and remains in a latent state until reactivated by different stimuli. When productive reactivations occur, the virus travels back along axons to the primary infection site, where new rounds of replication are initiated in the skin, in recurrent or secondary infections. During this process, new neuron infections occur. Noteworthy, the mechanisms underlying viral reactivations and the exit of latency are somewhat poorly understood and may be regulated by a crosstalk between the infected neurons and components of the immune system. Here, we review and discuss the immune responses that occur at the skin during primary and recurrent infections by HSV-1, as well as at the interphase of latently-infected neurons. Moreover, we discuss the implications of neuronal signals over the priming and migration of immune cells in the context of HSV-1 infection.

Association between tachyarrhythmia and mortality in a cohort of critically ill patients with coronavirus disease 2019 (COVID-19)

Background

Cardiovascular involvement manifesting as arrhythmias has been confirmed in patients with coronavirus disease 2019 (COVID-19), so we aimed to explore the association between primary tachyarrhythmia and death in critically ill patients with COVID-19 in this retrospective study.

Methods

A total of 79 critically ill patients with COVID-19 were included. Demographic characteristics, clinical data (past history, vital signs, therapeutic management, and outcomes), and results of laboratory findings and cardiac investigations were collected. All statistical analyses were performed using SPSS 23.0 software (IBM, Armonk, NY, USA).

Results

The median age was 65±12 years, and 53 patients (67%) were male. A total of 57 (72%) patients died, and compared with survivors, these patients were older and had significantly higher Acute Physiology and Chronic Health Evaluation (APACHE) II score, Sequential Organ Failure Assessment (SOFA) score and fewer lymphocytes as well as higher heart rate (P<0.05). Autopsy findings did not suggest severe myocarditis. A total of 19 (24%) patients had tachyarrhythmias, including 10 (13%) with atrial fibrillation (AF) and 9 (11%) with ventricular tachycardia or fibrillation. The incidence of tachyarrhythmias in non-survivor was much higher than in survivors (P=0.04). In a Cox regression model, older patients with ventricular tachyarrhythmias (VTAs) age were at a higher risk of death, with hazard ratio (HR) of 3.302 [95% confidence interval (CI), 1.524-7.154, P=0.002] and 1.045 (95% CI, 1.020-1.071, P=0.000), respectively. The use of beta-blockers [HR, 0.219 (95% CI, 0.066-0.722); P=0.013] was associated with a lower risk of death.

Conclusions

Critically ill patients with COVID-19 had a poor prognosis. VTA and older age were independent prognostic factors of death. Beta-blockers might be an effective therapy to improve survival.

Possible effect of epinephrine in minimizing COVID-19 severity: a review

OBJECTIVE

Coronavirus disease 2019 (COVID-19) shows a wide range of severity, ranging from an asymptomatic presentation to a severe illness requiring intensive care unit admission. Identification of a strategy to manage the severity of this disease will not only help to reduce its case fatality but also help to remove some of the burden from the already overwhelmed health care systems. While successful management of symptoms in general is important, identifying measures to modify the severity of the illness is a key factor in the fight against this pandemic.

METHODS

This paper presents a short literature review to suggest a new treatment modality for COVID-19.

RESULTS

COVID-19 is less severe and rarely fatal in children than in adults, which could be caused by greater fluctuations of plasma epinephrine in children. Our literature survey endorses this hypothesis according to both the epidemiological and immunological findings.

CONCLUSION

Application of epinephrine pulses with a specific amplitude may be considered an intervention to minimize the severity of COVID-19.

Genomic, microbial and environmental standardization in animal experimentation limiting immunological discovery

Background

The use of inbred mice housed under standardized environmental conditions has been critical in identifying immuno-pathological mechanisms in different infectious and inflammatory diseases as well as revealing new therapeutic targets for clinical trials. Unfortunately, only a small percentage of preclinical intervention studies using well-defined mouse models of disease have progressed to clinically-effective treatments in patients. The reasons for this lack of bench-to-bedside transition are not completely understood; however, emerging data suggest that genetic diversity and housing environment may greatly influence muring immunity and inflammation.

Results

Accumulating evidence suggests that certain immune responses and/or disease phenotypes observed in inbred mice may be quite different than those observed in their outbred counterparts. These differences have been thought to contribute to differing immune responses to foreign and/or auto-antigens in mice vs. humans. There is also a growing literature demonstrating that mice housed under specific pathogen free conditions possess an immature immune system that remarkably affects their ability to respond to pathogens and/or inflammation when compared with mice exposed to a more diverse spectrum of microorganisms. Furthermore, recent studies demonstrate that mice develop chronic cold stress when housed at standard animal care facility temperatures (i.e. 22–24 °C). These temperatures have been shown alter immune responses to foreign and auto-antigens when compared with mice housed at their thermo-neutral body temperature of 30–32 °C.

Conclusions

Exposure of genetically diverse mice to a spectrum of environmentally-relevant microorganisms at housing temperatures that approximate their thermo-neutral zone may improve the chances of identifying new and more potent therapeutics to treat infectious and inflammatory diseases.

Beta-Adrenergic Signaling in Tumor Immunology and Immunotherapy

Communication between the nervous and immune systems is required for the body to regulate physiological homeostasis. Beta-adrenergic receptors expressed on immune cells mediate the modulation of immune response by neural activity. Activation of beta-adrenergic signaling results in suppression of antitumor immune response and limits the efficacy of cancer immunotherapy. Beta-adrenergic signaling is also involved in regulation of hematopoietic reconstitution, which is critical to the graft-versus-tumor (GVT) effect and to graft-versus-host disease (GVHD) following allogeneic hematopoietic cell transplantation (HCT). In this review, the function of beta-adrenergic signaling in mediating tumor immunosuppression will be highlighted. We will also discuss the implication of targeting beta-adrenergic signaling to improve the efficacy of cancer immunotherapy including the GVT effect, and to diminish the adverse effects including GVHD.

Contribution of Immune Cells to Glucocorticoid Receptor Expression in Breast Cancer

Breast cancer (BC) patients experience increased stress with elevated cortisol levels, increasing risk of cancer recurrence. Cortisol binds to a cytoplasmic receptor, glucocorticoid receptor (GR) encoded by GR gene (NR3C1). We hypothesized that not only cancer cells, but even immune cells in the tumor microenvironment (TME) may contribute to GR expression in bulk tumor and influence prognosis. To test this, mRNA expression data was accessed from METABRIC and TCGA. "High" and "low" expression was based on highest and lowest quartiles of NR3C1 gene expression, respectively. Single-cell sequencing data were obtained from GSE75688 and GSE114725 cohorts. Computer algorithms CIBERSORT, Gene Set Enrichment Analysis and TIMER were used. GR-high BC has better median disease-free and disease-specific survival. Single cell sequencing data showed higher GR expression on immune cells compared to cancer and stromal cells. Positive correlation between GR-high BC and CD8⁺ T-cells was noted. In GR-high tumors, higher cytolytic activity (CYT) with decreased T-regulatory and T-follicular helper cells was observed. High GR expression was associated with lower proliferation index Ki67, enriched in IL-2_STAT5, apoptosis, KRAS, TGF-β signaling, and epithelial-to-mesenchymal transition. Immune cells significantly contribute to GR expression of bulk BC. GR-high BC has a favorable TME with higher CYT with favorable outcomes.

β2-Adrenergic receptor activation on donor cells ameliorates acute GvHD

Acute graft versus host disease (aGvHD) remains a major impediment to successful allogeneic hematopoietic cell transplantation (allo-HCT). To solve this problem, a greater knowledge of factors that regulate the differentiation of donor T cells toward cytotoxic cells or Tregs is necessary. We report that the β2-adrenergic receptor (β2-AR) is critical for regulating this differentiation and that its manipulation can control aGvHD without impairing the graft-versus-tumor (GvT) effect. Donor T cell β2-AR expression and signaling is associated with decreased aGvHD when compared with recipients of β2-AR-/- donor T cells. We determined that β2-AR activation skewed CD4+ T cell differentiation in vitro and in vivo toward Tregs rather than the T helper 1 (Th1) phenotype. Treatment of allo-HCT recipients with a selective β2-agonist (bambuterol) ameliorated aGvHD severity. This was associated with increased Tregs, decreased cytotoxic T cells, and increased donor BM-derived myeloid-derived suppressor cells (MDSCs) in allogeneic and humanized xenogeneic aGvHD models. β2-AR signaling resulted in increased Treg generation through glycogen synthase kinase-3 activation. Bambuterol preserved the GvT effect by inducing NKG2D+ effector cells and central memory T cells. These data reveal how β-AR signaling can be targeted to ameliorate GvHD severity while preserving GvT effect.

Beta-adrenergic receptor stimulation influences the function of monocytes/macrophages in ayu (Plecoglossus altivelis)

Adrenergic receptors (ARs) are members of the G-protein-coupled receptor superfamily that can be categorized into αARs and βARs. The specific function of ARs in teleost monocytes/macrophages (MO/MФ) remains unknown. We determined the cDNA sequence of ARs from ayu (Plecoglossus altivelis; PaαAR and PaβAR). Sequence comparisons showed that PaαAR was most closely related to the αAR of the Japanese flounder and Nile tilapia, while PaβAR was most closely related to the βAR of Atlantic salmon. The AR transcripts were mainly expressed in the spleen, and their expression was altered in various tissues upon infection with Vibrio anguillarum. PaαAR and PaβAR proteins were upregulated in MO/MФ after infection, and PaβAR knockdown resulted in a pro-inflammatory status in ayu MO/MФ upon V. anguillarum infection and lowered the phagocytic activity of MO/MФ. Our results indicate that PaβAR plays the role of an anti-inflammatory mediator in the immune response of ayu against bacterial infection.

Renal denervation restrains the inflammatory response in myocardial ischemia-reperfusion injury

Myocardial ischemia-reperfusion (I/R) injury leads to intensive sympathetic nervous system (SNS) activation and inflammatory reactions. Whether renal sympathetic denervation (RDN) could be a new therapeutic strategy to modulate I/R inflammation and reduce infarct size after myocardial I/R injury needs to be explored. First, we investigated the correlation between plasma norepinephrine concentrations and circulating myeloid cell numbers in patients with acute myocardial infarction. And then, C57BL/6 mice underwent a "two-hit" operation, with 10% phenol applied to bilateral renal nerves to abrogate sympathoexcitation, and a 45-min ligation of the left coronary artery to induce myocardial I/R injury. The effects of RDN on the mobilization of immune cells in mice following myocardial I/R injury were explored. We observed a strong association between SNS overactivation and myeloid cell excessive accumulation in patients. In animal experiments, there was a significant reduction in infarct size per area at risk in the denervated-I/R group when compared to that of the innervated-I/R group (39.2% versus 49.8%; p < 0.005), and RDN also improved the left ventricular ejection fraction by 20% after 1 week. Furthermore, the denervated-I/R group showed a decrease in the number of neutrophils and macrophages in the blood and the myocardium as reflected by immunohistochemical staining and flow cytometry analysis (p < 0.05); the decrease was associated with a significant reduction in the circulating production of IL-1, IL-6 and TNF-α (p < 0.05). In summary, our study reveals a novel link between the SNS activity and inflammatory response undergoing myocardium I/R injury and identifies RDN as a potential therapeutic strategy against myocardium I/R injury via preserving the spleen immune cells mobilization.

Manipulation of Ambient Housing Temperature To Study the Impact of Chronic Stress on Immunity and Cancer in Mice

Mice are the preeminent research organism in which to model human diseases and study the involvement of the immune response. Rapidly accumulating evidence indicates a significant involvement of stress hormones in cancer progression, resistance to therapies, and suppression of immune responses. As a result, there has been a concerted effort to model human stress in mice. In this article, we discuss recent literature showing how mice in research facilities are chronically stressed at baseline because of environmental factors. Focusing on housing temperature, we suggest that the stress of cool housing temperatures contributes to the impact of other imposed experimental stressors and therefore has a confounding effect on mouse stress models. Furthermore, we propose that manipulation of housing temperature is a useful approach for studying the impact of chronic stress on disease and the immune response and for testing therapeutic methods of reducing the negative effects of chronic stress.

Defining Early Life Stress as a Precursor for Autoimmune Disease

Childhood exposure to traumatic events, termed early life stress (ELS), is now widely recognized for causing long-term negative health effects that may not manifest until adulthood. Allostatic load (AL) describes the cumulative "wear-and-tear" effects of chronic stress on the body that may adversely affect human health by accelerating other disease processes. Recent epidemiological studies have reported higher stress levels in industrialized countries and trends of increasing prevalence in autoimmune diseases during recent decades. To elucidate mechanisms of stress-related immune dysregulation, most animal studies up to now have focused on AL and stress-triggered events occurring in adults but have not explored ELS in the context of autoimmune disorders. We have identified a current gap in understanding the impact of ELS on immune system ontogeny and its potential for priming genetically susceptible individuals who are at increased risk for autoimmune diseases later in life, through mechanisms involving neuroendocrine-immune cross talk. In this review, we highlight the intersection between stress and immune function, with a focus on ELS as consequential for increased autoimmune disorder risks later in life.

The β2-adrenergic receptor controls inflammation by driving rapid IL-10 secretion

The mammalian nervous system communicates important information about the environment to the immune system, but the underlying mechanisms are largely unknown. Secondary lymphoid organs are highly innervated by sympathetic neurons that secrete norepinephrine (NE) as the primary neurotransmitter. Immune cells express adrenergic receptors, enabling the sympathetic nervous system to directly control immune function. NE is a potent immunosuppressive factor and markedly inhibits TNF-α secretion from innate cells in response to lipopolysaccharide (LPS). In this study, we demonstrate that NE blocks the secretion of a variety of proinflammatory cytokines by rapidly inducing IL-10 secretion from innate cells in response to multiple Toll-like receptor (TLR) signals. NE mediated these effects exclusively through the β2-adrenergic receptor (ADRB2). Consequently, Adrb2^-/- animals were more susceptible to L. monocytogenes infection and to intestinal inflammation in a dextran sodium sulfate (DSS) model of colitis. Further, Adrb2^-/- animals rapidly succumbed to endotoxemia in response to a sub-lethal LPS challenge and exhibited elevated serum levels of TNF-α and reduced IL-10. LPS-mediated lethality in WT animals was rescued by administering a β 2-specific agonist and in Adrb2^-/- animals by exogenous IL-10. These findings reveal a critical role for ADRB2 signaling in controlling inflammation through the rapid induction of IL-10. Our findings provide a fundamental insight into how the sympathetic nervous system controls a critical facet of immune function through ADRB2 signaling.

α-Synuclein and Noradrenergic Modulation of Immune Cells in Parkinson's Disease Pathogenesis

α-synuclein (α-syn) pathology and loss of noradrenergic neurons in the locus coeruleus (LC) are among the most ubiquitous features of Parkinson's disease (PD). While noradrenergic dysfunction is associated with non-motor symptoms of PD, preclinical research suggests that the loss of LC norepinephrine (NE), and subsequently its immune modulatory and neuroprotective actions, may exacerbate or even accelerate disease progression. In this review, we discuss the mechanisms by which α-syn pathology and loss of central NE may directly impact brain health by interrupting neurotrophic factor signaling, exacerbating neuroinflammation, and altering regulation of innate and adaptive immune cells.

Adrenergic Signaling: A Targetable Checkpoint Limiting Development of the Antitumor Immune Response

An immune response must be tightly controlled so that it will be commensurate with the level of response needed to protect the organism without damaging normal tissue. The roles of cytokines and chemokines in orchestrating these processes are well known, but although stress has long been thought to also affect immune responses, the underlying mechanisms were not as well understood. Recently, the role of nerves and, specifically, the sympathetic nervous system, in regulating immune responses is being revealed. Generally, an acute stress response is beneficial but chronic stress is detrimental because it suppresses the activities of effector immune cells while increasing the activities of immunosuppressive cells. In this review, we first discuss the underlying biology of adrenergic signaling in cells of both the innate and adaptive immune system. We then focus on the effects of chronic adrenergic stress in promoting tumor growth, giving examples of effects on tumor cells and immune cells, explaining the methods commonly used to induce stress in preclinical mouse models. We highlight how this relates to our observations that mandated housing conditions impose baseline chronic stress on mouse models, which is sufficient to cause chronic immunosuppression. This problem is not commonly recognized, but it has been shown to impact conclusions of several studies of mouse physiology and mouse models of disease. Moreover, the fact that preclinical mouse models are chronically immunosuppressed has critical ramifications for analysis of any experiments with an immune component. Our group has found that reducing adrenergic stress by housing mice at thermoneutrality or treating mice housed at cooler temperatures with β-blockers reverses immunosuppression and significantly improves responses to checkpoint inhibitor immunotherapy. These observations are clinically relevant because there are numerous retrospective epidemiological studies concluding that cancer patients who were taking β-blockers have better outcomes. Clinical trials testing whether β-blockers can be repurposed to improve the efficacy of traditional and immunotherapies in patients are on the horizon.