Immune dysregulation in chronic stress: a quantitative and functional assessment of regulatory T cells

Role of transforming growth factor-β1 pathway in angiogenesis induced by chronic stress in colorectal cancer

BACKGROUND

Chronic stress can induce stress-related hormones; norepinephrine (NE) is considered to have the highest potential in cancer. NE can stimulate the expression of hypoxia-inducible factor-1α (HIF-1α), which is associated with vascular endothelial growth factor (VEGF) secretion and tumor angiogenesis. However, the underlying mechanisms are poorly understood.

METHODS

Tumor-bearing mice were subjected to chronic restraint stress and treated with normal saline, human monoclonal VEGF-A neutralizing antibody bevacizumab, or β-adrenergic receptor (β-AR) antagonist (propranolol). Tumor growth and vessel density were also evaluated. Human colorectal adenocarcinoma cells were treated with NE, propranolol, or the inhibitor of transforming growth factor-β (TGF-β) receptor Type I kinase (Ly2157299) in vitro. TGF-β1 in mouse serum and cell culture supernatants was quantified using ELISA. The expression of HIF-1α was measured using Real time-PCR and western blotting. Cell migration and invasion were tested.

RESULTS

Chronic restraint stress attenuated the efficacy of bevacizumab and promoted tumor growth and angiogenesis in a colorectal tumor model. Propranolol blocked this effect and inhibited TGF-β1 elevation caused by chronic restraint stress or NE. NE upregulated HIF-1α expression, which was reversed by propranolol or Ly2157299. Propranolol and Ly2157199 blocked NE-stimulated cancer cell migration and invasion.

CONCLUSIONS

Our results demonstrate the effect of NE on tumor angiogenesis and the critical role of TGF-β1 signaling during this process. In addition, β-AR/TGF-β1 signaling/HIF-1α/VEGF is a potential signaling pathway. This study also indicates that psychosocial stress might be a risk factor which weakens the efficacy of anti-angiogenic therapy.

Lack of canonical thyroid hormone receptor α signaling changes regulatory T cell phenotype in female mice

The immune system has emerged as an important target of thyroid hormones (THs); however, the role of TH in T cells has so far remained elusive. In this study, we assessed the effect of TH receptor α (TRα) signaling on activation and function of T cells. Our findings show that lack of canonical TRα action not only increased the frequency of regulatory T cells (Treg) but propelled an activated and migratory Treg phenotype and nuclear factor κB (NF-κB) activation in Treg. Conversely, canonical TRα action reduced activation of the NF-κB pathway previously shown to play a pivotal role in Treg differentiation and function. Taken together, our findings demonstrate that TRα impacts T cell differentiation and phenotype. Given the well-known interaction of inflammation, immune responses, and TH axis in e.g., severe illness, altered TH-TRα signaling may have an important role in regulating T cell responses during disease.

Age-stratified comorbid and pharmacologic analysis of patients with glioblastoma

Background

Increased age is a strong and unfavorable prognostic factor for patients with glioblastoma (GBM). However, the relationships between stratified patient age, comorbidities, and medications have yet to be explored in GBM patient survival analyses.

Objective

To evaluate co-morbid conditions, tumor-related symptoms, medication prescriptions, and subject age for patients with GBM and to establish potential targets for prospective studies.

Methods

Electronic health records for 565 patients with IDHwt GBM were evaluated at a single center between January 1, 2000 and August 9, 2021 were retrospectively assessed. Data were stratified by MGMT promoter methylation status when available and were used to construct multivariable time-dependent cox models and intra-cohort hazards.

Results

Younger (<65 years of age) but not older (≥65 years) GBM patients demonstrated a worse prognosis with movement related disabilities (P < 0.0001), gait/balance difficulty (P = 0.04) and weakness (P = 0.007), as well as psychiatric conditions, mental health disorders (P = 0.002) and anxiety (P = 0.001). In contrast, older but not younger GBM patients demonstrated a worse prognosis with epilepsy (P = 0.039). Both groups had worse survival with confusion/altered mental status (P = 0.023 vs < 0.000) and an improved survival with a Temozolomide prescription. Older but not younger GBM patients experienced an improved hazard with a prescription of ace-inhibitor medications (P = 0.048).

Conclusion

Age-dependent novel associations between clinical symptoms and medications prescribed for co-morbid conditions were demonstrated in patients with GBM. The results of the current work support future mechanistic studies that investigate the negative relationship(s) between increased age, comorbidities, and drug therapies for differential clinical decision-making across the lifespan of patients with GBM.

Treg cell: Critical role of regulatory T-cells in depression

Depression is a highly prevalent disorder of the central nervous system. The neuropsychiatric symptoms of clinical depression are persistent and include fatigue, anorexia, weight loss, altered sleep patterns, hyperalgesia, melancholia, anxiety, and impaired social behaviours. Mounting evidences suggest that neuroinflammation triggers dysregulated cellular immunity and increases susceptibility to psychiatric diseases. Neuroimmune responses have transformed the clinical approach to depression because of their roles in its pathophysiology and their therapeutic potential. In particular, activated regulatory T (Treg) cells play an increasingly evident role in the inflammatory immune response. In this review, we summarized the available data and discussed in depth the fundamental roles of Tregs in the pathogenesis of depression, as well as the clinical therapeutic potential of Tregs. We aimed to provide recent information regarding the potential of Tregs as immune-modulating biologics for the treatment and prevention of long-term neuropsychiatric symptoms of depression.

Neuro faces of beneficial T cells: essential in brain, impaired in aging and neurological diseases, and activated functionally by neurotransmitters and neuropeptides

T cells are essential for a healthy life, performing continuously: immune surveillance, recognition, protection, activation, suppression, assistance, eradication, secretion, adhesion, migration, homing, communications, and additional tasks. This paper describes five aspects of normal beneficial T cells in the healthy or diseased brain. First, normal beneficial T cells are essential for normal healthy brain functions: cognition, spatial learning, memory, adult neurogenesis, and neuroprotection. T cells decrease secondary neuronal degeneration, increase neuronal survival after central nervous system (CNS) injury, and limit CNS inflammation and damage upon injury and infection. Second, while pathogenic T cells contribute to CNS disorders, recent studies, mostly in animal models, show that specific subpopulations of normal beneficial T cells have protective and regenerative effects in several neuroinflammatory and neurodegenerative diseases. These include Multiple Sclerosis (MS), Alzheimer's disease, Parkinson's disease, Amyotrophic Lateral Sclerosis (ALS), stroke, CNS trauma, chronic pain, and others. Both T cell-secreted molecules and direct cell-cell contacts deliver T cell neuroprotective, neuroregenerative and immunomodulatory effects. Third, normal beneficial T cells are abnormal, impaired, and dysfunctional in aging and multiple neurological diseases. Different T cell impairments are evident in aging, brain tumors (mainly Glioblastoma), severe viral infections (including COVID-19), chronic stress, major depression, schizophrenia, Parkinson's disease, Alzheimer's disease, ALS, MS, stroke, and other neuro-pathologies. The main detrimental mechanisms that impair T cell function are activation-induced cell death, exhaustion, senescence, and impaired T cell stemness. Fourth, several physiological neurotransmitters and neuropeptides induce by themselves multiple direct, potent, beneficial, and therapeutically-relevant effects on normal human T cells, via their receptors in T cells. This scientific field is called "Nerve-Driven Immunity". The main neurotransmitters and neuropeptides that induce directly activating and beneficial effects on naïve normal human T cells are: dopamine, glutamate, GnRH-II, neuropeptide Y, calcitonin gene-related peptide, and somatostatin. Fifth, "Personalized Adoptive Neuro-Immunotherapy". This is a novel unique cellular immunotherapy, based on the "Nerve-Driven Immunity" findings, which was recently designed and patented for safe and repeated rejuvenation, activation, and improvement of impaired and dysfunctional T cells of any person in need, by ex vivo exposure of the person's T cells to neurotransmitters and neuropeptides. Personalized adoptive neuro-immunotherapy includes an early ex vivo personalized diagnosis, and subsequent ex vivo → in vivo personalized adoptive therapy, tailored according to the diagnosis. The Personalized Adoptive Neuro-Immunotherapy has not yet been tested in humans, pending validation of safety and efficacy in clinical trials, especially in brain tumors, chronic infectious diseases, and aging, in which T cells are exhausted and/or senescent and dysfunctional.

Origin of Sex-Biased Mental Disorders: Do Males and Females Experience Different Selective Regimes?

The origins of sex-biased differences in disease and health are of growing interest to both medical researchers and health professionals. Several major factors have been identified that affect sex differences in incidence of diseases and mental disorders. These are: sex chromosomes, sex hormones and female immunity, sexual selection and antagonistic evolution, and differential susceptibility of sexes to environmental factors. These factors work on different time scales and are not exclusive of each other. Recently, a combined Sexual Selection-Sex Hormones (SS-SH) Theory was presented as an evolutionary mechanism to explain sex-biased differences in diseases and mental disorders (Singh in J Mol Evol 89:195-213, 2021). In that paper disease prevalence trends were investigated, and non-sex-specific diseases were hypothesized to be more common in males than in females in general. They showed signs of exceptions to this trend with inflammatory diseases and stress-related mental disorders that were more common in females. We believe that the SS-SH theory requires the consideration of psycho-social stress (PSS) to explain the predominance of female-biased mental disorders and some other exceptions in their findings. Here we present a theory of sex-differential experience of PSS and provide quantitative support for the combined SS-SH-PSS Theory using age-standardized incidence rates (ASIRs) recording the levels of male- and female-bias in data obtained from different countries. The grand theory provides an evolutionary framework for explaining patterns of sex-biased trends in the prevalence of disease and health. Further exploration of women's vulnerability to social factors may help to facilitate new treatments for female-biased diseases.

Neurotransmitters and Neuropeptides decrease PD-1 in T cells of healthy subjects and patients with hepatocellular carcinoma (HCC), and increase their proliferation and eradication of HCC cells

T cells of aged people, and of patients with either cancer or severe infections (including COVID-19), are often exhausted, senescent and dysfunctional, leading to increased susceptibilities, complications and mortality. Neurotransmitters and Neuropeptides bind their receptors in T cells, and induce multiple beneficial T cell functions. Yet, T cells of different people vary in the expression levels of Neurotransmitter and Neuropeptide receptors, and in the magnitude of the corresponding effects. Therefore, we performed an individual-based study on T cells of 3 healthy subjects, and 3 Hepatocellular Carcinoma (HCC) patients. HCC usually develops due to chronic inflammation. The inflamed liver induces reduction and inhibition of CD4⁺ T cells and Natural Killer (NK) cells. Immune-based therapies for HCC are urgently needed. We tested if selected Neurotransmitters and Neuropeptides decrease the key checkpoint protein PD-1 in human T cells, and increase proliferation and killing of HCC cells. First, we confirmed human T cells express all dopamine receptors (DRs), and glutamate receptors (GluRs): AMPA-GluR3, NMDA-R and mGluR. Second, we discovered that either Dopamine, Glutamate, GnRH-II, Neuropeptide Y and/or CGRP (10nM), as well as DR and GluR agonists, induced the following effects: 1. Decreased significantly both %PD-1⁺ T cells and PD-1 expression level per cell (up to 60% decrease, within 1 h only); 2. Increased significantly the number of T cells that proliferated in the presence of HCC cells (up to 7 fold increase), 3. Increased significantly T cell killing of HCC cells (up to 2 fold increase). 4. Few non-conventional combinations of Neurotransmitters and Neuropeptides had surprising synergistic beneficial effects. We conclude that Dopamine, Glutamate, GnRH-II, Neuropeptide Y and CGRP, alone or in combinations, can decrease % PD-1⁺ T cells and PD-1 expression per cell, in T cells of both healthy subjects and HCC patients, and increase their proliferation in response to HCC cells and killing of HCC cells. Yet, testing T cells of many more cancer patients is absolutely needed. Based on these findings and previous ones, we designed a novel "Personalized Adoptive Neuro-Immunotherapy", calling for validation of safety and efficacy in clinical trials.

T Cells Plead for Rejuvenation and Amplification; With the Brain's Neurotransmitters and Neuropeptides We Can Make It Happen

T cells are essential for eradicating microorganisms and cancer and for tissue repair, have a pro-cognitive role in the brain, and limit Central Nervous System (CNS) inflammation and damage upon injury and infection. However, in aging, chronic infections, acute SARS-CoV-2 infection, cancer, chronic stress, depression and major injury/trauma, T cells are often scarce, exhausted, senescent, impaired/biased and dysfunctional. People with impaired/dysfunctional T cells are at high risk of infections, cancer, other diseases, and eventually mortality, and become multi-level burden on other people, organizations and societies. It is suggested that “Nerve-Driven Immunity” and “Personalized Adoptive Neuro-Immunotherapy” may overcome this problem. Natural Neurotransmitters and Neuropeptides: Glutamate, Dopamine, GnRH-II, CGRP, Neuropeptide Y, Somatostatin and others, bind their well-characterized receptors expressed on the cell surface of naïve/resting T cells and induce multiple direct, beneficial, and therapeutically relevant effects. These Neurotransmitters and Neuropeptides can induce/increase: gene expression, cytokine secretion, integrin-mediated adhesion, chemotactic migration, extravasation, proliferation, and killing of cancer. Moreover, we recently found that some of these Neurotransmitters and Neuropeptides also induce rapid and profound decrease of PD-1 in human T cells. By inducing these beneficial effects in naïve/resting T cells at different times after binding their receptors (i.e. NOT by single effect/mechanism/pathway), these Neurotransmitters and Neuropeptides by themselves can activate, rejuvenate, and improve T cells. “Personalized Adaptive Neuro-Immunotherapy” is a novel method for rejuvenating and improving T cells safely and potently by Neurotransmitters and Neuropeptides, consisting of personalized diagnostic and therapeutic protocols. The patient’s scarce and/or dysfunctional T cells are activated ex vivo once by pre-selected Neurotransmitters and/or Neuropeptides, tested, and re-inoculated to the patient’s body. Neuro-Immunotherapy can be actionable and repeated whenever needed, and allows other treatments. This adoptive Neuro-Immunotherapy calls for testing its safety and efficacy in clinical trials.

Influence of cortisol awakening response on telomere length: Trends for males and females

Although telomere attrition is associated with the process of normal ageing, shorter telomere length (TL) has been associated with acute and chronic stressors. A neurobiological factor hypothesised to be responsible for this accelerated attrition is the dysregulation of the cortisol stress response, which can induce DNA damage affecting DNA telomeric caps. Marked sex differences are reported in both the cortisol stress response and telomere dynamics, yet no explicit investigation of sex specificity on the relationship between cortisol and TL exists. This study used mathematical equation modelling to describe the relationship between diurnal cortisol levels and telomere length within the context of sex, in a healthy population. Cortisol awakening responses (CAR) were measured via ELISA methodology in fifty-one healthy participants (28 males, 23 females). qPCRs determined TL from genomic DNA extracted from saliva. To assess the effect of free cortisol on relative TL ratio, a semi-log regression plot of the two variables trended for sex were fitted using spline curves. Results demonstrated significant differences between males and females in the relationship defining CAR and TL association (p = 0.03). These results suggest the relationship is not linear and can be represented as a complex arcsin function, and that the patterns are opposite in males and females. Males demonstrate a positive correlation, with higher levels of CAR being associated with longer telomere sequences. Females demonstrated a negative correlation. Future studies must carefully take into consideration moderating factors such as sex, and sex hormones across the lifespan when investigating telomere length.

Social Defeat Modulates T Helper Cell Percentages in Stress Susceptible and Resilient Mice

Altered adaptive immunity involving T lymphocytes has been found in depressed patients and in stress-induced depression-like behavior in animal models. Peripheral T cells play important roles in homeostasis and function of the central nervous system and thus modulate behavior. However, the T cell phenotype and function associated with susceptibility and resilience to depression remain largely unknown. Here, we characterized splenic T cells in susceptible and resilient mice after 10 days of social defeat stress (SDS). We found equally decreased T cell frequencies and comparably altered expression levels of genes associated with T helper (Th) cell function in resilient and susceptible mice. Interleukin (IL)-17 producing CD4⁺ and CD8⁺ T cell numbers in the spleen were significantly increased in susceptible mice. These animals further exhibited significantly reduced numbers of regulatory T cells (T_reg) and decreased gene expression levels of TGF-β. Mice with enhanced Th17 differentiation induced by conditional deletion of PPARγ in CD4⁺ cells (CD4-PPARγ^KO), an inhibitor of Th17 development, were equally susceptible to SDS when compared to CD4-PPARγ^WT controls. These data indicate that enhanced Th17 differentiation alone does not alter stress vulnerability. Thus, SDS promotes Th17 cell and suppresses T_reg cell differentiation predominantly in susceptible mice with yet unknown effects in immune responses after stress exposure.

Alterations of the Innate Immune System in Susceptibility and Resilience After Social Defeat Stress

Dysregulation of innate immune responses has frequently been reported in stress-associated psychiatric disorders such as major depression. In mice, enhanced circulating cytokine levels as well as altered innate immune cell numbers have been found after stress exposure. In addition, stress-induced recruitment of peripheral monocytes to the brain has been shown to promote anxiety-like behavior. However, it is yet unclear whether specific differences in the innate immune system are associated with stress susceptibility or resilience in mice. Utilizing chronic social defeat, a model of depression and stress vulnerability, we characterized peripheral and brain-invading myeloid cells in stress-susceptible and resilient animals. In all defeated animals, we found reduced percentages of CD11c⁺ dendritic cells (DCs) by flow cytometry in the spleen when compared to non-defeated controls. Exclusively in susceptible mice conventional DCs of the spleen showed up-regulated expression of MHC class II and co-stimulatory CD80 molecules pointing toward an enhanced maturation phenotype of these cells. Susceptible, but not resilient animals further exhibited an increase in inflammatory Ly6C^hi monocytes and higher numbers of spleen-derived CD11b⁺ cells that produced the proinflammatory cytokine tumor necrosis factor (TNF) upon lipopolysaccharide (LPS) stimulation. Increased percentages of peripheral CD45^hi CD11b⁺ cells immigrated into the brain of defeated mice, regardless of resilience or susceptibility. However, cellular infiltrates in the brain of susceptible mice contained higher percentages of CC chemokine receptor 2 (CCR2⁺) Ly6C^hi monocytes representing an inflammatory phenotype. Thus, we defined specific stress-related immune signatures involving conventional DCs and inflammatory Ly6C^hi monocytes in susceptible and resilient mice. Together, our findings suggest an impact of the innate immune system in vulnerability to stress-related disorders such as major depression.

Acute stress promotes post-injury brain regeneration in fish

The central nervous system and the immune system, the two major players in homeostasis, operate in the ongoing bidirectional interaction. Stress is the third player that exerts strong effect on these two 'supersystems'; yet, its impact is studied much less. In this work employing carp model, we studied the influence of preliminary stress on neural and immune networks involved in post-injury brain regeneration. The relevant in vivo models of air-exposure stress and precisely directed cerebellum injury have been developed. Neuronal regeneration was evaluated by using specific tracers of cell proliferation and differentiation. Involvement of immune networks was accessed by monitoring the expression of selected T cells markers. Contrast difference between acute and chronic stress manifested in the fact that chronically stressed fish did not survive the brain injury. Neuronal regeneration appeared as a biphasic process whereas involvement of immune system proceeded as a monophasic route. In stressed fish, immune response was fast and accompanied or even preceded neuronal regeneration. In unstressed subjects, immune response took place on the second phase of neuronal regeneration. These findings imply an intrinsic regulatory impact of acute stress on neuronal and immune factors involved in post-injury brain regeneration. Stress activates both neuronal and immune defense mechanisms and thus contributes to faster regeneration. In this context, paradoxically, acute preliminary stress might be considered a distinct asset in speeding up the following post-injury brain regeneration.

Induction of Suppressor Cells and Increased Tumor Growth following Chronic Psychosocial Stress in Male Mice

To study the impact of psychosocial stress on the immune system, male mice were subjected to chronic subordinate colony housing (CSC), a preclinically validated mouse model for chronic psychosocial stress. CSC substantially affected the cell composition of the bone marrow, blood, and spleen by inducing myelopoiesis and enhancing the frequency of regulatory T cells in the CD4 population. Expansion of the myeloid cell compartment was due to cells identified as immature inflammatory myeloid cells having the phenotype of myeloid-derived suppressor cells of either the granulocytic or the monocytic type. Catecholaminergic as well as TNF signaling were implicated in these CSC-induced cellular shifts. Although the frequency of regulatory cells was enhanced following CSC, the high capacity for inflammatory cytokine secretion of total splenocytes indicated an inflammatory immune status in CSC mice. Furthermore, CSC enhanced the suppressive activity of bone marrow-derived myeloid-derived suppressor cells towards proliferating T cells. In line with the occurrence of suppressor cell types such as regulatory T cells and myeloid-derived suppressor cells, transplanted syngeneic fibrosarcoma cells grew better in CSC mice than in controls, a process accompanied by pronounced angiogenesis and clustering of immature myeloid cells in the tumor tissue. In addition, tumor implantation after CSC reinforced the CSC-induced increase in myeloid-derived suppressor cells and regulatory T cell frequencies while the CSC-induced cellular changes eased off in mice without tumor. Together, our data suggest a role for suppressor cells such as regulatory T cells and myeloid-derived suppressor cells in the enhanced tumor growth after chronic psychosocial stress.

Increased percentages of regulatory T cells are associated with inflammatory and neuroendocrine responses to acute psychological stress and poorer health status in older men and women

RATIONALE

The percentage of regulatory T cells (TRegs)-a subtype of T lymphocyte that suppresses the immune response-appears to be reduced in a number of stress-related diseases. The role of the TReg in stress-disease pathways has not yet been investigated.

OBJECTIVES

The aim of the study was to investigate the association between biological responsivity to acute psychosocial stress and the percentage of TRegs in healthy older adults. The secondary purpose was to measure the associations between TReg percentage and psychological and physical well-being in the participants.

METHODS

Salivary cortisol and plasma interleukin (IL)-6 samples were obtained from 121 healthy older men and women from the Whitehall II cohort following acute psychophysiological stress testing. Three years later at a follow-up visit, we measured TReg percentages and psychological and physical well-being were recorded using the Short Form 36 Health Survey and the Center for Epidemiologic Studies Depression Scale.

RESULTS

Blunted cortisol responses (p = 0.004) and elevated IL-6 responses (p = 0.027) to acute psychophysiological stress were associated with greater TReg percentage independently of age, sex, BMI, smoking status, employment grade, time of testing, and baseline measures of cortisol and IL-6, respectively. Percentage of TRegs was associated cross-sectionally with lower physical (p = 0.043) and mental health status (p = 0.008), and higher levels of depressive symptoms (p = 0.002), independently of covariates.

CONCLUSIONS

Increased levels of TRegs may act as a defence against increased inflammation and may be a pre-indication for chronically stressed individuals on the cusp of clinical illness.

Sleep-deprivation reduces NK cell number and function mediated by β-adrenergic signalling

Reduction of sleep time triggers a stress response, leading to augmented levels of glucocorticoids and adrenaline. These hormones regulate components of the innate immune system such as natural killer (NK) and NKT cells. In the present study, we sought to investigate whether and how stress hormones could alter the population and function of NK and NKT cells of mice submitted to different lengths of paradoxical sleep deprivation (PSD, from 24 to 72 h). Results showed that 72h of PSD decreased not only NK and NKT cell counts, but also their cytotoxic activity against B16F10 melanoma cells in vitro. Propranolol treatment during PSD reversed these effects, indicating a major inhibitory role of beta-adrenergic receptors (β-AR) on NK cells function. Moreover, both corticosterone plasma levels and expression of beta 2-adrenergic receptors (β2-AR) in NK cells increased by 48 h of PSD. In vitro incubation of NK cells with dexamethasone augmented the level of β2-AR in the cell surface, suggesting that glucocorticoids could induce β2-AR expression. In summary, we propose that reduction of NK and NKT cell number and cytotoxic activity appears to be mediated by glucocorticoids-induced increased expression of β2-AR in these cells.

Stimulation of the histamine 4 receptor with 4-methylhistamine modulates the effects of chronic stress on the Th1/Th2 cytokine balance

Alterations to the immune system caused by stress have been considered to markedly increase the risk for immune-related diseases such as cancer and autoimmune disorders. We investigated the potential anti-stress effects of the histamine 4 receptor (H4R) agonist, 4-methylhistamine (4-MeH), in a murine stress model. Mice were placed in 50ml conical centrifuge tubes for 12h followed by a 12h rest. The effects of treatment with 4-MeH (30mg/kg, i.p., twice daily) for 2 days were assessed. At 2 days after physical restraint, mice were sacrificed and tissues harvested. We evaluated the effects of 4-MeH treatment on CD4(+) T cell production, and intracellular IFN-γ and IL-4 expression in these cells. We also assessed IL-1β, IFN-γ, TNF-α, and IL-4 mRNA expression as well as IFN-γ, TNF-α, GITR, Ox40 and IL-4 protein expression in the spleen. The results showed that 4-MeH treatment of stressed mice results in a substantial increase in the CD4(+) T cells as well as in IFN-γ production by these cells. Compared to both untreated and stressed controls. In contrast, IL-4 expression decreased significantly following 4-MeH treatment of mice. Moreover, stimulation of the H4R resulted in up-regulated expression of IL-1β, IFN-γ and TNF-α mRNAs and decreased the expression of IL-4. Western blot analysis confirmed decreased protein expression of IFN-γ, TNF-α, GITR, Ox40 and increased IL-4 in the SC group and treatment of mice with 4-MeH reversed these effects. Our results confirm the significant impact of chronic stress on T cell function and production of Th1/Th2 mediators H4R.

Attenuation of experimental colitis in glutathione peroxidase 1 and catalase double knockout mice through enhancing regulatory T cell function

Reactive oxygen species (ROS) have been implicated in the progression of inflammatory diseases including inflammatory bowel diseases (IBD). Meanwhile, several studies suggested the protective role of ROS in immune-mediated inflammatory diseases, and it was recently reported that dextran sodium sulfate (DSS)-induced colitis was attenuated in mice with an elevated level of ROS due to deficiency of peroxiredoxin II. Regulatory T cells (Tregs) are critical in the prevention of IBD and Treg function was reported to be closely associated with ROS level, but it has been investigated only in lowered levels of ROS so far. In the present study, in order to clarify the relationship between ROS level and Treg function, and their role in the pathogenesis of IBD, we investigated mice with an elevated level of ROS due to deficiency of both glutathione peroxidase (GPx)-1 and catalase (Cat) for the susceptibility of DSS-induced colitis in association with Treg function. The results showed that DSS-induced colitis was attenuated and Tregs were hyperfunctional in GPx1^−/− × Cat^−/− mice. In vivo administration of N-acetylcysteine (NAC) aggravated DSS-induced colitis and decreased Treg function to the level comparable to WT mice. Attenuated Th₁₇ cell differentiation from naïve CD4⁺ cells as well as impaired production of IL-6 and IL-17A by splenocytes upon stimulation suggested anti-inflammatory tendency of GPx1^−/− × Cat^−/− mice. Suppression of Stat3 activation in association with enhancement of indoleamine 2,3-dioxygenase and FoxP3 expression might be involved in the immunosuppressive mechanism of GPx1^−/− × Cat^−/− mice. Taken together, it is implied that ROS level is critical in the regulation of Treg function, and IBD may be attenuated in appropriately elevated levels of ROS.

Essential role of IL-10/STAT3 in chronic stress-induced immune suppression

Stress can either enhance or suppress immune functions depending on a variety of factors such as duration of stressful condition. Chronic stress has been demonstrated to exert a significant suppressive effect on immune function. However, the mechanisms responsible for this phenomenon remain to be elucidated. Here, male C57BL/6 mice were placed in a 50-ml conical centrifuge tube with multiple punctures to establish a chronic restraint stress model. Serum IL-10 levels, IL-10 production by the splenocytes, and activation of STAT3 in the mouse spleen were assessed. We demonstrate that IL-10/STAT3 axis was remarkably activated following chronic stress. Moreover, TLR4 and p38 MAPK play a pivotal role in the activation of IL-10/STAT3 signaling cascade. Interestingly, blocking antibody against IL-10 receptor and inhibition of STAT3 by STAT3 inhibitor S3I-201 attenuates stress-induced lymphocyte apoptosis. Inhibition of IL-10/STAT3 dramatically inhibits stress-induced reduction in IL-12 production. Furthermore, disequilibrium of Th1/Th2 cytokine balance caused by chronic stress was also rescued by blocking IL-10/STAT3 axis. These results yield insight into a new mechanism by which chronic stress regulates immune functions. IL-10/STAT3 pathway provides a novel relevant target for the manipulation of chronic stress-induced immune suppression.

Stimulatory Toll-like receptor 2 suppresses restraint stress-induced immune suppression

Stress can enhance or suppress immune functions depending on a variety of factors. Our previous studies observed that Toll-like receptor 2 (TLR2) participates in chronic restraint stress-induced immune dysfunction. However, the mechanism by which TLR2 prevents immune suppression remains elusive. Our investigation found that stimulation of TLR2 by peptidoglycan (PGN) significantly attenuates splenocyte apoptosis and markedly blocks alterations of anti-apoptotic and apoptotic proteins. Activation of TLR2 inhibits chronic stress-reduced phosphorylation of c-Jun N-terminal kinase (JNK) and diminishes chronic stress-induced up-regulation of corticosterone production. Additionally, our data show that chronic stress causes a dramatic decrease of cytokine IL-2 level but an increase of IL-4 and IL-17 in CD4(+) T cells. Interestingly, PGN could block these alterations of cytokine levels. Collectively, our studies demonstrate that stimulation of TLR2 attenuates chronic stress-induced immune suppression by modulating apoptosis-related proteins and immunoregulatory agents.

The impact of self-reported psychological stress levels on changes to peripheral blood immune biomarkers in recreational marathon runners during training and recovery

OBJECTIVE

Marathon training is both physically and psychologically stressful, both of which can lead to altered immunity. The purpose of this study was to determine if the overall immunoregulatory changes associated with the physical stress of marathon training are affected by psychological stress.

METHODS

Nineteen recreational marathoners completed the Perceived Stress Scale (PSS), State-Trait Anxiety Inventory (STAI) and Penn State Worry Questionnaire (PSWQ), and had levels of T cell subpopulations and cytokine (IFNγ, IL4 and IL10) production determined 4 weeks before (baseline), 24-48 h before (prerace) and 1 week after (recovery) participation in a marathon.

RESULTS

PSS scores decreased at the prerace visit compared to baseline and remained low at recovery. Compared to baseline, there were significant changes to numerous immune measures at the prerace visit, including decreases in Th1/Th2 ratio, Tc1/Tc2 ratio, Tr1 and Th3 cell populations as well as decreases in IFNγ/IL4 cytokine ratio and IL10 production. Most immune parameters had returned to near baseline values at the recovery visit. Higher levels of perceived stress, anxiety and worry exacerbated many of the alterations in immunity that were observed at the prerace visit. Higher levels of perceived stress and worry had significant effects on changes to Treg, IL4 production and the IFNγ/IL4 cytokine ratio. Stress had an additional impact on changes in IL10 production. High anxiety levels resulted in significant changes to Treg, Tr1 and Th3.

CONCLUSION

These data suggest that recreational marathon runners with higher levels of psychological stress may be more at risk for the immune alterations that are common during periods of prolonged physical training.