Impacts of Immunometabolism on Male Reproduction.

The physiological process of male reproduction relies on the orchestration of neuroendocrine, immune, and energy metabolism. Spermatogenesis is controlled by the hypothalamic-pituitary-testicular (HPT) axis, which modulates the production of gonadal steroid hormones in the testes. The immune cells and cytokines in testes provide a protective microenvironment for the development and maturation of germ cells. The metabolic cellular responses and processes in testes provide energy production and biosynthetic precursors to regulate germ cell development and control testicular immunity and inflammation. The metabolism of immune cells is crucial for both inflammatory and anti-inflammatory responses, which supposes to affect the spermatogenesis in testes. In this review, the role of immunometabolism in male reproduction will be highlighted. Obesity, metabolic dysfunction, such as type 2 diabetes mellitus, are well documented to impact male fertility; thus, their impacts on the immune cells distributed in testes will also be discussed. Finally, the potential significance of the medicine targeting the specific metabolic intermediates or immune metabolism checkpoints to improve male reproduction will also be reassessed.

Enhancing Effects of Environmental Enrichment on the Functions of Natural Killer Cells in Mice.

The environment of an organism can convey a powerful influence over its biology. Environmental enrichment (EE), as a eustress model, has been used extensively in neuroscience to study neurogenesis and brain plasticity. EE has also been used as an intervention for the treatment and prevention of neurological and psychiatric disorders with limited clinical application. By contrast, the effects of EE on the immune system are relatively less investigated. Recently, accumulating evidence has demonstrated that EE can robustly impact immune function. In this review, we summarize the major components of EE, the impact of EE on natural killer (NK) cells, EE's immunoprotective roles in cancer, and the underlying mechanisms of EE-induced NK cell regulation. Moreover, we discuss opportunities for translational application based on insights from animal research of EE-induced NK cell regulation.

Loss of vagal integrity disrupts immune components of the microbiota-gut-brain axis and inhibits the effect of Lactobacillus rhamnosus on behavior and the corticosterone stress response.

The vagus nerve is one of the major signalling components between the gut microbiota and brain. However, the exact relationship between gut-brain signaling along the vagus and the effects of gut microbes on brain function and behaviour is unclear. In particular, the relationship between the vagus nerve and immune signaling, that also appears to play a critical role in microbiota-gut-brain communication, has not been delineated. The aim of the present study was to determine the effect of subdiaphragmatic vagotomy on peripheral and central immune changes associated with the anxiolytic actions of L.rhamnosus. Male mice underwent vagotomy or sham surgery, followed by administration of L.rhamnosus for 14 days. L.rhamnosus administration following sham surgery resulted in reduced anxiety-like behaviour, and an attenuation of the hypothalamic-pituitary-adrenal axis (HPA axis), as indicated by reduced plasma corticosterone after acute restraint stress. These effects were associated with an increase in splenic T regulatory cells and a decrease in activated microglia in the hippocampus. The anxiolytic effects, HPA modulation and increase in T regulatory cells were prevented by vagotomy, whereas vagotomy alone led to a significant increase in activated microglia in the hippocampus that was not altered with L.rhamnosus treatment. Thus, both microbe induced and constitutive vagal signaling influences critical immune components of the microbiota-gut-brain axis. These findings suggest that, rather than acting as a direct neural link to the central nervous system, the role of the vagus nerve in gut-microbe to brain signalling is as an integral component of a bi-directional neuroimmunoendocrine pathway.

Role of enhanced glucocorticoid receptor sensitivity in inflammation in PTSD: insights from computational model for circadian-neuroendocrine-immune interactions.

Although glucocorticoid resistance contributes to increased inflammation, individuals with posttraumatic stress disorder (PTSD) exhibit increased glucocorticoid receptor (GR) sensitivity along with increased inflammation. It is not clear how inflammation coexists with a hyperresponsive hypothalamic-pituitary-adrenal (HPA) axis. To understand this better, we developed and analyzed an integrated mathematical model for the HPA axis and the immune system. We performed mathematical simulations for a dexamethasone (DEX) suppression test and IC50-dexamethasone for cytokine suppression by varying model parameters. The model analysis suggests that increasing the steepness of the dose-response curve for GR activity may reduce anti-inflammatory effects of GRs at the ambient glucocorticoid levels, thereby increasing proinflammatory response. The adaptive response of proinflammatory cytokine-mediated stimulatory effects on the HPA axis is reduced due to dominance of the GR-mediated negative feedback on the HPA axis. To verify these hypotheses, we analyzed the clinical data on neuroendocrine variables and cytokines obtained from war-zone veterans with and without PTSD. We observed significant group differences for cortisol and ACTH suppression tests, proinflammatory cytokines TNFα and IL6, high-sensitivity C-reactive protein, promoter methylation of GR gene, and IC50-DEX for lysozyme suppression. Causal inference modeling revealed significant associations between cortisol suppression and post-DEX cortisol decline, promoter methylation of human GR gene exon 1F (NR3C1-1F), IC50-DEX, and proinflammatory cytokines. We noted significant mediation effects of NR3C1-1F promoter methylation on inflammatory cytokines through changes in GR sensitivity. Our findings suggest that increased GR sensitivity may contribute to increased inflammation; therefore, interventions to restore GR sensitivity may normalize inflammation in PTSD.

Neuroinflammation and depressive disorder: The role of the hypothalamus.

Data accumulated over the last two decades has demonstrated that hypothalamic inflammation plays an important role in the etiopathogenesis of the most prevalent diseases, such as cardiovascular diseases, metabolic syndrome, and even cancer. Recent findings indicate that hypothalamic inflammation is also associated with stress exposure and certain psychiatric diseases, such as depressive disorder. Mechanistic studies have shown that intense and/or chronic stress exposure is accompanied by the synthesis of inflammatory molecules in the hypothalamus, altered hypothalamic-pituitary-adrenal axis activity, and development of glucocorticoid resistance. Consequently, these factors might play a role in the etiopathogenesis of psychiatric disorders. We propose that hypothalamic inflammation represents an interconnection between somatic diseases and depressive disorder. These assumptions are discussed in this mini-review in the light of available data from studies focusing on hypothalamic inflammation.

Remitted depression and cognition in HIV: The role of cortisol and inflammation.

In major depressive disorder (MDD) and remitted MDD (rMDD) alterations in cortisol and inflammation are associated with cognitive difficulties, but these relationships have not been investigated in HIV. We used secondary data from a placebo-controlled, cross-over study of cognitive performance following a probe of the hypothalamic-pituitary-adrenal (HPA) axis (low dose hydrocortisone; LDH 10 mg) in 65 people with HIV (PWH; 36 women). Using placebo data, we examined sex-specific associations between two biomarkers - basal afternoon salivary cortisol and salivary inflammatory cytokines - cognition, and rMDD. Salivary cortisol and inflammatory biomarkers were sampled across the 5 -h study. The panel of inflammatory markers included interleukin (IL)-6, IL-8, IL-1ß, tumor necrosis factor-(TNF)-α, CRP, interferon gamma-induced protein (IP-10), monocyte chemotactic protein (MCP)-1, monokine induced by interferon (MIG), matrix metalloproteinase MMP-9, and MMP-1. Learning, memory, attention/concentration, and executive function were assessed 30 min and 4 h after the placebo intervention; visuospatial ability was also assessed 30 min after the placebo intervention. For women but not men with HIV, basal cortisol concentrations were higher in rMDD versus noMDD groups, and related to poorer learning and memory. For men and women with HIV, basal inflammatory cytokines were higher in rMDD versus noMDD groups, but were negatively related to cognition independent of rMDD status. Cortisol and cytokines relate to cognition in PWH, but the associations depended on sex, rMDD status, and their interaction.

An anti-CRF antibody suppresses the HPA axis and reverses stress-induced phenotypes.

Hypothalamic-pituitary-adrenal (HPA) axis dysfunction contributes to numerous human diseases and disorders. We developed a high-affinity monoclonal antibody, CTRND05, targeting corticotropin-releasing factor (CRF). In mice, CTRND05 blocks stress-induced corticosterone increases, counteracts effects of chronic variable stress, and induces other phenotypes consistent with suppression of the HPA axis. CTRND05 induces skeletal muscle hypertrophy and increases lean body mass, effects not previously reported with small-molecule HPA-targeting pharmacologic agents. Multiorgan transcriptomics demonstrates broad HPA axis target engagement through altering levels of known HPA-responsive transcripts such as Fkbp5 and Myostatin and reveals novel HPA-responsive pathways such as the Apelin-Apelin receptor system. These studies demonstrate the therapeutic potential of CTRND05 as a suppressor of the HPA axis and serve as an exemplar of a potentially broader approach to target neuropeptides with immunotherapies, as both pharmacologic tools and novel therapeutics.

Immunization against Kisspeptin-54 perturb hypothalamic-pituitary-testicular signaling pathway in ram lambs.

Kisspeptin, a peptide product of KISS1 gene, recently identified as essential upstream gatekeeper in hypothalamic-pituitary-gonadal (HPG) axis. This study was designed to investigate the effect of immunization against kisspeptin-54 on hypothalamic-pituitary-testicular signaling pathway. A total of ten intact 56-days-old ram lambs were used and randomized into the treatment and control groups, which were, respectively immunized by kisspeptin-54 based vaccine and the empty plasmid via intramuscular route. We employed indirect enzyme-linked immunosorbent assay and quantitative real-time PCR to characterize the difference in serum kisspeptin, luteinizing hormone, testosterone hormone concentration and mRNA expression of reproductive-related genes in HPG axis across kisspeptin-54 immunized and control ram lambs. Serum kisspeptin, luteinizing hormone and testosterone concentration in the treatment group was lower (p < 0.05) than that of the control group. Compared with the control group, the mRNA expression of the hypothalamic androgen receptor (AR), KISS1, G protein-coupled receptor (GPR54) and gonadotropin-releasing hormone (GnRH) was altered in the immunized group (p < 0.05). Moreover, mRNA expression of pituitary luteinizing hormone beta (LHß), follicle stimulating hormone beta (FSHß), and GnRH receptor as well as, testicular LH receptor and FSH receptor, were remarkably lower (P < 0.05) in the treatment group. We concluded that immunization against kisspeptin-54 reduced serum kisspeptin levels thereby, the normal hypothalamic-pituitary-testicular signaling pathway disrupted. This data provides a great insight for the use of kisspeptin to regulate reproduction.

[Effects of endogenous glucocorticoid deprivation on immune response of allergic rhinitis in mice].

Objective: To study the effect of dysfunction of the hypothalamic-pituitary-adrenal (HPA) axis on the pathogenesis of allergic rhinitis (AR) by the mouse model of decreased endogenous glucocorticoid (GC) after adrenalectomy, and further explore the mechanism of neural-endocrine regulation. Methods: According to literatures, adrenalectomized (ADX) mice and AR model were established. Eighty mice were randomly divided into four groups (n=20 per group) including control group, AR group of normal mice (AR group), AR group of bilateral ADX (bilateral ADX/AR group) and AR group of unilateral ADX (unilateral ADX/AR group). In order to assess the model of ADX, adrenal gland tissue was assayed by HE staining and the plasma adrenocorticotropic hormone (ACTH) and cortisol (CORT) concentrations were measured by enzyme-linked immunosorbent assay (ELISA). The behavioral observation, OVA-sIgE assessments and count of eosinophils/mast cells by the HE/Toluidine Blue staining of nasal septum mucosa tissue were performed to evaluate the AR model. The expression of peripheral blood CD4(+) IL4(+) T cells (Th2 cells) and CD4(+) IFN-γ(+) T cells (Th1 cells), splenocytes of CD4(+) CD25(+) Treg cells (Treg cells) were measured by flow cytometry to study the influence of endogenous GC on immunological indexes in different groups of mice. SPSS 16.0 software was used to analyze the data. Results: The concentrations of OVA-sIgE in control group, AR group, bilateral ADX/AR group and unilateral ADX/AR group mice were (28.86±3.62) ng/ml, (76.27±16.47) ng/ml, (48.37±8.89) ng/ml, (49.86±7.19) ng/ml, respectively. There was statistically significant difference between control group and AR group (t=7.09, P<0.05), AR group and bilateral ADX/AR group (t=4.81, P<0.05), AR group and unilateral ADX/AR group (t=5.21, P<0.05). The level of Th2 cells in different four groups were (0.71±0.24)%, (7.03±1.95)%, (2.44±2.06)%, (3.20±1.21)%, respectively. There was statistically significant difference between control group and AR group (t=-2.93, P<0.05), AR group and bilateral ADX/AR group (t=-4.67, P<0.05), AR group and unilateral ADX/AR group (t=-3.61, P<0.05). The expression of Th2 in bilateral ADX/AR group is lower than that in unilateral ADX/AR group without significant difference (t=4.39, P>0.05). Meanwhile, the level of Th1 cells in different four groups was (0.58±0.76)%, (0.57±0.59)%, (0.72±0.34)%, (1.03±0.32)%, respectively, with no significant difference among these groups. The proportion of Treg cells was (11.10±2.18)%, (4.10±1.07)%, (7.15±0.92)%, (4.58±1.05)%, respectively, with significant difference between control and other groups (t value was -7.171, -8.273, -8.360, respectively, all P<0.05). Compared with AR group, Treg cells increased significantly in bilateral ADX/AR group (t=-2.607, P<0.05). In addition, lower expression of eosinophil and mast cell were detected in the local nasal tissue of bilateral ADX/AR group, and mast cell degranulation wasn't be observed. Conclusion: Unilateral or bilateral ADX leads to HPA axis dysfunction and endogenous GC deprivation, possibly regulating the mechanism of AR through Th1/Th2 immune bias and Tregs cell' activity.

How stress contributes to autoimmunity-lessons from Sjögren's syndrome.

A large body of clinical evidence on the association between stressful life events and autoimmune diseases suggests that stress may play an important role in the pathogenesis of these disorders. In this article, we discuss the effects of stress, not on the immune system but on specific cell populations against which the autoimmune reactivity is directed. Using Sjögren's syndrome as a model autoimmune disease, we review the role of stress in the initiation and perpetuation of autoimmune reactivity. We present data that reveal the effects of stress on salivary gland epithelial cells, suggesting that stress can become immunogenic through its various effects on salivary gland epithelium.

The role of hypothalamic inflammation, the hypothalamic-pituitary-adrenal axis and serotonin in the cancer anorexia-cachexia syndrome.

PURPOSE OF REVIEW: In cancer patients, the development of cachexia (muscle wasting) is frequently aggravated by anorexia (loss of appetite). Their concurrence is often referred to as anorexia-cachexia syndrome. This review focusses on the recent evidence underlining hypothalamic inflammation as key driver of these processes. Special attention is given to the involvement of hypothalamic serotonin. RECENT FINDINGS: The anorexia-cachexia syndrome is directly associated with higher mortality in cancer patients. Recent reports confirm its severe impact on the quality of life of patients and their families.Hypothalamic inflammation has been shown to contribute to muscle and adipose tissue loss in cancer via central hypothalamic interleukine (IL)1ß-induced activation of the hypothalamic-pituitary-adrenal axis. The resulting release of glucocorticoids directly stimulates catabolic processes in these tissues via activation of the ubiquitin-proteosome pathway. Next to this, hypothalamic inflammation has been shown to reduce food intake in cancer by triggering changes in orexigenic and anorexigenic responses via upregulation of serotonin availability and stimulation of its signalling pathways in hypothalamic tissues. This combination of reduced food intake and stimulation of tissue catabolism represents a dual mechanism by which hypothalamic inflammation contributes to the development and maintenance of anorexia and cachexia in cancer. SUMMARY: Hypothalamic inflammation is a driving force in the development of the anorexia-cachexia syndrome via hypothalamic-pituitary-adrenal axis and serotonin pathway activation.

Participation of hypothalamic CB1 receptors in reproductive axis disruption during immune challenge.

Immune challenge inhibits reproductive function and endocannabinoids (eCB) modulate sexual hormones. However, no studies have been performed to assess whether the eCB system mediates the inhibition of hormones that control reproduction as a result of immune system activation during systemic infections. For that reason, we evaluated the participation of the hypothalamic cannabinoid receptor CB1 on the hypothalamic-pituitary-gonadal (HPG) axis activity in rats submitted to immune challenge. Male adult rats were treated i.c.v. administration with a CB1 antagonist/inverse agonist (AM251) (500 ng/5 µL), followed by an i.p. injection of lipopolysaccharide (LPS) (5 mg/kg) 15 minutes later. Plasmatic, hypothalamic and adenohypophyseal pro-inflammatory cytokines, hormones and neuropeptides were assessed 90 or 180 minutes post-LPS. The plasma concentration of tumour necrosis factor α and adenohypophyseal mRNA expression of Tnfα and Il1ß increased 90 and 180 minutes post i.p. administration of LPS. However, cytokine mRNA expression in the hypothalamus increased only 180 minutes post-LPS, suggesting an inflammatory delay in this organ. CB1 receptor blockade with AM251 increased LPS inflammatory effects, particularly in the hypothalamus. LPS also inhibited the HPG axis by decreasing gonadotrophin-releasing hormone hypothalamic content and plasma levels of luteinising hormone and testosterone. These disruptor effects were accompanied by decreased hypothalamic Kiss1 mRNA expression and prostaglandin E2 content, as well as by increased gonadotrophin-inhibitory hormone (Rfrp3) mRNA expression. All these disruptive effects were prevented by the presence of AM251. In summary, our results suggest that, in male rats, eCB mediate immune challenge-inhibitory effects on reproductive axis at least partially via hypothalamic CB1 activation. In addition, this receptor also participates in homeostasis recovery by modulating the inflammatory process taking place after LPS administration.

Thermal imprinting modifies adult stress and innate immune responsiveness in the teleost sea bream.

The impact of thermal imprinting on the plasticity of the hypothalamic-pituitary-interrenal (HPI) axis and stress response in an adult ectotherm, the gilthead sea bream (Sparusaurata, L.), during its development was assessed. Fish were reared under 4 thermal regimes, and the resulting adults exposed to acute confinement stress and plasma cortisol levels and genes of the HPI axis were monitored. Changes in immune function, a common result of stress, were also evaluated using histomorphometric measurements of melanomacrophages centers (MMCs) in the head kidney and by monitoring macrophage-related transcripts. Thermal history significantly modified the HPI responsiveness in adult sea bream when eggs and larvae were reared at a higher than optimal temperature (HT, 22°C), and they had a reduced amplitude in their cortisol response and significantly upregulated pituitary pomc and head kidney star transcripts. Additionally, after an acute stress challenge, immune function was modified and the head kidney of adult fish reared during development at high temperatures (HT and LHT, 18-22°C) had a decreased number of MMCs and a significant downregulation of dopachrome tautomerase. Thermal imprinting during development influenced adult sea bream physiology and increased plasma levels of glucose and sodium even in the absence of an acute stress in fish reared under a high-low thermal regime (HLT, 22-18°C). Overall, the results demonstrate that temperature during early development influences the adult HPI axis and immune function in a teleost fish.

Regulation of hypothalamic-pituitary-adrenal axis activity and immunologic function contributed to the anti-inflammatory effect of acupuncture in the OVA-induced murine asthma model.

Asthma is a complex inflammatory disease of the airways and acupuncture is one of the effective therapies widely used to treat asthma in China. The aim of the study was to evaluate the regulatory role of acupuncture in airway inflammation and the hypothalamic-pituitary-adrenal (HPA) axis activity in OVA-induced murine asthma model. Our results demonstrated that acupuncture was effective in suppression of AHR, inhibition of total leukocyte, neutrophil, lymphocyte and eosinophil counts in BALF, attenuation of airway inflammation and TNF-α, IL-1ß, IL-5 and eotaxin secretion. Furthermore, the HPA axis activity was also regulated by acupuncture, which included promotion of adrenocorticotropic hormone and cortisol secretion in the plasma. Our findings revealed that acupuncture could attenuate airway inflammation and regulate HPA axis and immunologic function in the OVA-induced murine asthma model, which may provide support to better understand the contribution of acupuncture to the regulation of airway inflammation and HPA axis activity in asthma.

Hypothalamic-Pituitary-Adrenal Hypofunction in Myalgic Encephalomyelitis (ME)/Chronic Fatigue Syndrome (CFS) as a Consequence of Activated Immune-Inflammatory and Oxidative and Nitrosative Pathways.

There is evidence that immune-inflammatory and oxidative and nitrosative stress (O&NS) pathways play a role in the pathophysiology of myalgic encephalomyelitis (ME)/chronic fatigue syndrome (CFS). There is also evidence that these neuroimmune diseases are accompanied by hypothalamic-pituitary-adrenal (HPA) axis hypoactivity as indicated by lowered baseline glucocorticoid levels. This paper aims to review the bidirectional communications between immune-inflammatory and O&NS pathways and HPA axis hypoactivity in ME/CFS, considering two possibilities: (a) Activation of immune-inflammatory pathways is secondary to HPA axis hypofunction via attenuated negative feedback mechanisms, or (b) chronic activated immune-inflammatory and O&NS pathways play a causative role in HPA axis hypoactivity. Electronic databases, i.e., PUBMED, Scopus, and Google Scholar, were used as sources for this narrative review by using keywords CFS, ME, cortisol, ACTH, CRH, HPA axis, glucocorticoid receptor, cytokines, immune, immunity, inflammation, and O&NS. Findings show that activation of immune-inflammatory and O&NS pathways in ME/CFS are probably not secondary to HPA axis hypoactivity and that activation of these pathways may underpin HPA axis hypofunction in ME/CFS. Mechanistic explanations comprise increased levels of tumor necrosis factor-α, T regulatory responses with elevated levels of interleukin-10 and transforming growth factor-ß, elevated levels of nitric oxide, and viral/bacterial-mediated mechanisms. HPA axis hypoactivity in ME/CFS is most likely a consequence and not a cause of a wide variety of activated immune-inflammatory and O&NS pathways in that illness.

Evidence for increased immune mobilization in First Episode Psychosis compared with the prodromal stage in males.

The aim of the study was to gauge both the immune and neuroendocrine function in Ultra High Risk for psychosis (UHR) subjects and compare them with a cohort presenting with First Episode Psychosis (FEP). We recruited two groups, the first group consisted of 12 UHR males and the second of 25 males with FEP. We measured serum cortisol levels at 08:00, 12:00, 18:00 with their Area Under Curve with respect to the ground (AUCg) and the increase (AUCi) and we measured serum cytokines levels, Interleukin-1a, IL-1a, IL-2, IL-4,IL-5,IL-6,IL-8, IL-10,IL-12, IL-17a, Tumor Necrosis Factor-a (TNF-a), Interferon-γ (IFN-γ). Dexamethasone Suppression Test (DST) was also performed . The results suggest higher levels of both pro-inflammatory (TNF-a, IL-2, IL-12, IFN-γ) and anti-inflammatory (IL-10) cytokines in the FEP group compared with the UHR counterparts. Regarding the HPA axis function, the prodromal subjects showed a trend for higher AUCg and AUCi change/decrease cortisol levels. On the contrary, the DST results did not differ between the groups. No significant associations were demonstrated within each group among cytokines, cortisol and psychopathology. The findings favor a hypothesis of a relatively increased mobilization of both the pro- and anti-inflammatory cytokine networks, in FEP compared with that of UHR subjects.

Evaluation of pituitary function after infectious meningitis in childhood.

BACKGROUND: A number of studies of adults have shown that pituitary deficiencies can develop in a considerable proportion of subjects during the acute phase of meningitis or years after the infection has disappeared. The results of the very few studies of the impact of pediatric meningitis on hypothalamic-pituitary function are conflicting. METHODS: In order to determine the incidence of pituitary dysfunction in children with central nervous system infection, we evaluated pituitary function and anthropometric parameters in 19 children with meningitis of different etiologies (15 males; mean age ± standard deviation [SD] at pituitary evaluation, 5.9 ± 4.0 years; mean time from the acute event ± SD, 18 ± 10 months). RESULTS: All of the subjects had a normal stature and growth velocity for their age and gender, and none of them was obese. On the basis of Tanner's reference charts, 17 subjects (13 boys and all four girls) were pre-pubertal; two boys were in Tanner stage 2. None of the subjects had central hypothyroidism. All of the patients had normal serum of insulin growth factor (IGF)-I and prolactin. Their sex steroid and gonadotropin levels were concordant with their age and pubertal status. Early morning urine osmolality and serum electrolyte levels showed no signs of diabetes insipidus. All of the patients had normal plasma adrenocorticotropic hormone (ACTH) levels. Peak cortisol responses to the standard dose Synacthen test (SDST) were normal in all cases. CONCLUSIONS: The results showed that hypopituitarism following infectious meningitis appears to be infrequent in childhood and children's pituitary glands seem to be less vulnerable to damage than those of adults.

Probiotics normalize the gut-brain-microbiota axis in immunodeficient mice.

The gut-brain-microbiota axis is increasingly recognized as an important regulator of intestinal physiology. Exposure to psychological stress causes activation of the hypothalamic-pituitary-adrenal (HPA) axis and causes altered intestinal barrier function, intestinal dysbiosis, and behavioral changes. The primary aim of this study was to determine whether the effects of psychological stress on intestinal physiology and behavior, including anxiety and memory, are mediated by the adaptive immune system. Furthermore, we wanted to determine whether treatment with probiotics would normalize these effects. Here we demonstrate that B and T cell-deficient Rag1(-/-) mice displayed altered baseline behaviors, including memory and anxiety, accompanied by an overactive HPA axis, increased intestinal secretory state, dysbiosis, and decreased hippocampal c-Fos expression. Both local (intestinal physiology and microbiota) and central (behavioral and hippocampal c-Fos) changes were normalized by pretreatment with probiotics, indicating an overall benefit on health conferred by changes in the microbiota, independent of lymphocytes. Taken together, these findings indicate a role for adaptive immune cells in maintaining normal intestinal and brain health in mice and show that probiotics can overcome this immune-mediated deficit in the gut-brain-microbiota axis.

Interleukin-1ß induced activation of the hypothalamus-pituitary-adrenal axis is dependent on interleukin-1 receptors on non-hematopoietic cells.

The proinflammatory cytokine interleukin-1ß (IL-1ß) plays a major role in the signal transduction of immune stimuli from the periphery to the central nervous system, and has been shown to be an important mediator of the immune-induced stress hormone release. The signaling pathway by which IL-1ß exerts this function involves the blood-brain-barrier and induced central prostaglandin synthesis, but the identity of the blood-brain-barrier cells responsible for this signal transduction has been unclear, with both endothelial cells and perivascular macrophages suggested as critical components. Here, using an irradiation and transplantation strategy, we generated mice expressing IL-1 type 1 receptors (IL-1R1) either in hematopoietic or non-hematopoietic cells and subjected these mice to peripheral immune challenge with IL-1ß. Following both intraperitoneal and intravenous administration of IL-1ß, mice lacking IL-1R1 in hematopoietic cells showed induced expression of the activity marker c-Fos in the paraventricular hypothalamic nucleus, and increased plasma levels of ACTH and corticosterone. In contrast, these responses were not observed in mice with IL-1R1 expression only in hematopoietic cells. Immunoreactivity for IL-1R1 was detected in brain vascular cells that displayed induced expression of the prostaglandin synthesizing enzyme cyclooxygenase-2 and that were immunoreactive for the endothelial cell marker CD31, but was not seen in cells positive for the brain macrophage marker CD206. These results imply that activation of the HPA-axis by IL-1ß is dependent on IL-1R1s on non-hematopoietic cells, such as brain endothelial cells, and that IL-1R1 on perivascular macrophages are not involved.