Stress and immunological phagocytosis: possible nongenomic action of corticosterone

The Impact of Mouse Preterm Birth Induction by RU-486 on Microglial Activation and Subsequent Hypomyelination

Preterm birth (PTB) represents 15 million births every year worldwide and is frequently associated with maternal/fetal infections and inflammation, inducing neuroinflammation. This neuroinflammation is mediated by microglial cells, which are brain-resident macrophages that release cytotoxic molecules that block oligodendrocyte differentiation, leading to hypomyelination. Some preterm survivors can face lifetime motor and/or cognitive disabilities linked to periventricular white matter injuries (PWMIs). There is currently no recommendation concerning the mode of delivery in the case of PTB and its impact on brain development. Many animal models of induced-PTB based on LPS injections exist, but with a low survival rate. There is a lack of information regarding clinically used pharmacological substances to induce PTB and their consequences on brain development. Mifepristone (RU-486) is a drug used clinically to induce preterm labor. This study aims to elaborate and characterize a new model of induced-PTB and PWMIs by the gestational injection of RU-486 and the perinatal injection of pups with IL-1beta. A RU-486 single subcutaneous (s.c.) injection at embryonic day (E)18.5 induced PTB at E19.5 in pregnant OF1 mice. All pups were born alive and were adopted directly after birth. IL-1beta was injected intraperitoneally from postnatal day (P)1 to P5. Animals exposed to both RU-486 and IL-1beta demonstrated microglial reactivity and subsequent PWMIs. In conclusion, the s.c. administration of RU-486 induced labor within 24 h with a high survival rate for pups. In the context of perinatal inflammation, RU-486 labor induction significantly decreases microglial reactivity in vivo but did not prevent subsequent PWMIs.

Immune function and serum vitamin D in shelter dogs: A case-control study

This study sought to establish a baseline understanding of immune function and its association with serum vitamin D in shelter dogs. Ten apparently healthy shelter dogs housed in the Arizona Humane Society for ≥7 days and 10 apparently healthy, age, breed, and sex-matched control dogs were included. Serum 25-hydroxyvitamin D (25[OH]D), the major circulating vitamin D metabolite, was measured using high performance liquid chromatography. Whole blood samples were stimulated with lipopolysaccharide (LPS), lipoteichoic acid, or phosphate buffer solution, and tumor necrosis factor (TNF)-ɑ, interleukin (IL)-6, and IL-10 were measured using a canine-specific multiplex bead-based assay. Phagocytosis of opsonized-Escherichia coli and E. coli-induced oxidative burst were evaluated with flow cytometry. Shelter dogs had decreased percentages of granulocytes and monocytes (GM) that had phagocytized opsonized-E coli (P = 0.019) and performed E. coli-induced oxidative burst (P = 0.011). There were no significant differences in TNF-α, IL-6, IL-10, or 25(OH)D concentrations between shelter and control dogs. Serum 25(OH)D concentrations had a weak positive association with the intensity of GM E. coli-induced oxidative burst (r² = 0.23, P = 0.03). There was a moderate inverse association between serum 25(OH)D concentration and LPS-stimulated TNF-ɑ production in shelter dogs (r² = 0.40, P = 0.04). These results demonstrate immune dysregulation in vitro in shelter dogs housed for ≥7 days when compared to age, breed, and sex-matched control dogs. While serum 25(OH)D concentrations did not differ between shelter and control dogs, significant associations between 25(OH)D concentration and immune function parameters in vitro were identified.

More Than Suppression: Glucocorticoid Action on Monocytes and Macrophages

Uncontrolled inflammation is a leading cause of many clinically relevant diseases. Current therapeutic strategies focus mainly on immunosuppression rather than on the mechanisms of inflammatory resolution. Glucocorticoids (GCs) are still the most widely used anti-inflammatory drugs. GCs affect most immune cells but there is growing evidence for cell type specific mechanisms. Different subtypes of monocytes and macrophages play a pivotal role both in generation as well as resolution of inflammation. Activation of these cells by microbial products or endogenous danger signals results in production of pro-inflammatory mediators and initiation of an inflammatory response. GCs efficiently inhibit these processes by down-regulating pro-inflammatory mediators from macrophages and monocytes. On the other hand, GCs act on “naïve” monocytes and macrophages and induce anti-inflammatory mediators and differentiation of anti-inflammatory phenotypes. GC-induced anti-inflammatory monocytes have an increased ability to migrate toward inflammatory stimuli. They remove endo- and exogenous danger signals by an increased phagocytic capacity, produce anti-inflammatory mediators and limit T-cell activation. Thus, GCs limit amplification of inflammation by repressing pro-inflammatory macrophage activation and additionally induce anti-inflammatory monocyte and macrophage populations actively promoting resolution of inflammation. Further investigation of these mechanisms should lead to the development of novel therapeutic strategies to modulate undesirable inflammation with fewer side effects via induction of inflammatory resolution rather than non-specific immunosuppression.

Heat stress decreases expression of the cytokines, avian β-defensins 4 and 6 and Toll-like receptor 2 in broiler chickens infected with Salmonella Enteritidis

A high ambient temperature is a highly relevant stressor in poultry production. Heat stress (HS) has been reported to reduce animal welfare, performance indices and increase Salmonella susceptibility. Salmonella spp. are major zoonotic pathogen that cause over 1 billion of human infections worldwide annually. Therefore, the current study was designed to analyze the effect of heat stress on Salmonella infection in chickens through modulation of the immune responses. Salmonella Enteritidis was inoculated via gavage at one day of age (10⁶cfu/mL). Heat stress 31±1°C was applied from 35 to 41 days of age. Broiler chickens were divided into the following groups of 12 chickens: control (C); heat stress (HS31°C); S. Enteritidis positive control (PC); and S. Enteritidis+heat stress (PHS31°C). We observed that heat stress increased corticosterone serum levels. Concomitantly heat stress decreased (1) the IgA and IFN-γ plasmatic levels; (2) the mRNA expression of IL-6, IL-12 in spleen and IL-1β, IL-10, TGF-β in cecal tonsils; (3) the mRNA expression of AvBD4 and AvBD6 in cecal tonsils; and (4) the mRNA expression of TLR2 in spleen and cecal tonsils of chickens infected with S. Enteritidis (PHS31°C group). Heat stress also increased Salmonella colonization in the crop and caecum as well as Salmonella invasion to the spleen, liver and bone marrow, showing a deficiency in the control of S. Enteritidis induced infection. Together, the present data suggested that heat stress activated hypothalamus-pituitary-adrenal (HPA) axis, as observed by the increase in the corticosterone levels, which in turn presumably decreases the immune system activity, leading to an impairment of the intestinal mucosal barrier and increasing chicken susceptibility to the invasion of different organs by S. Enteritidis .

Host stress physiology and Trypanosoma haemoparasite infection influence innate immunity in the woylie (Bettongia penicillata)

Understanding immune function is critical to conserving wildlife in view of infectious disease threats, particularly in threatened species vulnerable to stress, immunocompromise and infection. However, few studies examine stress, immune function and infection in wildlife. We used a flow cytometry protocol developed for human infants to assess phagocytosis, a key component of innate immunity, in a critically endangered marsupial, the woylie (Bettongia penicillata). The effects of stress physiology and Trypanosoma infection on phagocytosis were investigated. Blood and faecal samples were collected from woylies in a captive facility over three months. Trypanosoma status was determined using PCR. Faecal cortisol metabolites (FCM) were quantified by enzyme-immunoassay. Mean phagocytosis measured was >90%. An interaction between sex and FCM influenced the percentage of phagocytosing leukocytes, possibly reflecting the influence of sex hormones and glucocorticoids. An interaction between Trypanosoma status and FCM influenced phagocytosis index, suggesting that stress physiology and infection status influence innate immunity.

Effect of cold stress on immunity in rats

An increase in the morbidity of upper respiratory tract infections and the attack and exacerbation of autoimmune diseases has been observed to occur in the few days following sudden environmental temperature decreases, but the mechanisms for these phenomena are not well understood. To determine the effect of a sudden ambient temperature drop on the levels of stress hormones and T-lymphocyte cytokines in the plasma, the Toll-like receptor 4 (TLR4) expression of immunocompetent cells in rat spleens and the levels of regulatory T (Treg) cells in the peripheral blood, Sprague Dawley rats were divided into three groups of different ambient temperatures (20, 4 and −12°C). In each group, there were four observation time-points (1, 12, 24 and 48 h). Each ambient temperature group was subdivided into non-stimulation, lipopolysaccharide-stimulation and concanavalin A-stimulation groups. The levels of adrenocorticotropin (ACTH), epinephrine (EPI), angiotensin-II (ANG-II), interleukin-2 (IL-2), interferon-γ (IFN-γ), IL-4 and IL-10 in the plasma were determined using ELISA. The cellular expression levels of TLR4 and the presence of cluster of differentiation (CD)4⁺CD25⁺ and CD4⁺CD25⁺Forkhead box P3 (Foxp3)⁺ cells were determined using flow cytometry. The experiments demonstrated that the ACTH, EPI, ANG-II and IL-10 levels in the plasma were significantly increased at 4 and −12°C compared with those at 20°C, while the plasma levels of IFN-γ, IL-2 and IL-4, the TLR4 expression rates of immunocompetent cells in the rat spleen and the percentage of CD4⁺CD25⁺Foxp3⁺ Treg cells among the CD4⁺CD25⁺ Treg cells in the peripheral blood were decreased at 4 and −12°C compared with those at 20°C. These data indicate that cold stress affects the stress hormones and the innate and adaptive immunity functions in rats.

Evaluation of corticosterone and IL-1β, IL-6, IL-10 and TNF-α expression after 670-nm laser photobiomodulation in rats

The literature has shown that low-level laser therapy accelerates the repair of cutaneous wounds. However, there is a scarcity of scientific studies that characterise the possible systemic interference of laser photobiomodulation. The aim of this research was to quantitatively evaluate blood corticosterone levels and tissue cytokine expression in cutaneous wounds of rats treated with low-level laser therapy (semiconductor diode AsGaAl, continuous emission, 9 mW, 670 nm, 0.031 W/cm(2), beam with an output area of 0.28 cm(2)) and normal controls. A total of 36 male Wistar rats were used and randomly divided into two groups of 18 rats each. A standardised circular 6-mm-diameter wound was made in the dorsal skin region of each rat, and they were euthanised at 1, 6 and 12 h after cutaneous surgery. The blood was collected, and portions of cutaneous tissue and subcutaneous muscle were removed and cryopreserved. Corticosterone levels in the blood were measured by a radioimmunoassay technique; histological sections were submitted to the ELISA technique for analysis of tissue cytokine expression levels. At 6 h after surgery, a significant increase in corticosterone and a significant reduction in the levels of IL-1β and IL-6 in tissues of irradiated wounds were observed when compared to controls (p < 0.05). The levels of TNF-α and IL-10 expression were not significantly different between the groups at different time intervals. Thus, this study strongly suggests a systemic and local biomodulation of low-level laser therapy as indicated by the blood levels of corticosterone and the tissue expression of IL-1β and IL-6, respectively.

Chronic cold stress in mice induces a regulatory phenotype in macrophages: correlation with increased 11β-hydroxysteroid dehydrogenase expression

Susceptibility to infections, autoimmune disorders and tumor progression is strongly influenced by the activity of the endocrine and nervous systems in response to a stressful stimulus. When the adaptive system is switched on and off efficiently, the body is able to recover from the stress imposed. However, when the system is activated repeatedly or the activity is sustained, as during chronic or excessive stress, an allostatic load is generated, which can lead to disease over long periods of time. We investigated the effects of chronic cold stress in BALB/c mice (4°C/4 h daily for 7 days) on functions of macrophages. We found that chronic cold stress induced a regulatory phenotype in macrophages, characterized by diminished phagocytic ability, decreased TNF-α and IL-6 and increased IL-10 production. In addition, resting macrophages from mice exposed to cold stress stimulated spleen cells to produce regulatory cytokines, and an immunosuppressive state that impaired stressed mice to control Trypanosoma cruzi proliferation. These regulatory effects correlated with an increase in macrophage expression of 11β-hydroxysteroid dehydrogenase, an enzyme that converts inactive glucocorticoid into its active form. As stress is a common aspect of modern life and plays a role in the etiology of many diseases, the results of this study are important for improving knowledge regarding the neuro-immune-endocrine interactions that occur during stress and to highlight the role of macrophages in the immunosuppression induced by chronic stress.

Effect of academic psychological stress in post-graduate students: the modulatory role of cortisol on superoxide release by neutrophils

Experimental and clinical evidence shows that neutrophils play an important role in the mechanism of tissue injury in immune complex diseases through the generation of reactive oxygen species. In this study, we examined the influence of academic psychological stress in post-graduate students on the capacity of their blood neutrophils to release superoxide when stimulated by immune complexes bound to nonphagocytosable surfaces and investigated the modulatory effect of cortisol on this immune function. The tests were performed on the day before the final examination. The state-trait anxiety inventory questionnaire was used to examine whether this stressful event caused emotional distress. In our study, the psychological stress not only increased plasma cortisol concentration, but it also provoked a reduction in superoxide release by neutrophils. This decrease in superoxide release was accompanied by diminished mRNA expression for subunit p47(phox) of the phagocyte superoxide-generating nicotinamide adenine dinucleotide phosphate-oxidase. These inhibitory effects were also observed by in vitro exposure of neutrophils from control volunteers to 10(- 7) M hydrocortisone, and could be prevented by the glucocorticoid receptor antagonist RU-486. These results show that in a situation of psychological stress, the increased levels of cortisol could inhibit superoxide release by neutrophils stimulated by IgG immune complexes bound to nonphagocytosable surfaces, which could attenuate the inflammatory state.

Blockade of mineralocorticoid and glucocorticoid receptors reverses stress-induced motor impairments

AIM

Stress and glucocorticoids can influence movement performance and pathologies of the motor system. The classic notion assumes that the glucocorticoid receptor (GR) mediates the majority of stress-induced behavioral changes. Nevertheless, recent findings have attributed a more prominent role to the mineralocorticoid receptor (MR) in modulating behavior. The purpose of this study was to dissociate the impact of MR versus GR activation in movement and stress-associated motor disruption.

METHODS

Groups of male and female rats were tested in skilled reaching and open field behavior and treated peri-orally with either agonists or antagonists for MR and GR, respectively.

RESULTS

Selective acute activation of MR (aldosterone) and GR (dexamethasone) decreased movement success with a magnitude similar to stress-induced impairment in male and female animals. By contrast, antagonist treatment to block MR (RU-28318) or GR (Mifepristone, RU-486) prevented motor impairments caused by acute restraint stress or corticosterone treatment. Moreover, both antagonists reversed chronic stress- and glucocorticoid-induced motor impairments to values comparable to baseline levels. Higher success rates in treated animals were accompanied by improved performance of skilled limb movements. In addition, combined treatment with MR and GR antagonists had additive benefit on aim and advance towards the reaching target.

CONCLUSION

These observations suggest that MR or GR equally influence motor system function with partially synergistic effects. Males and females show comparable responses to MR and GR activation or blockade. The need for balanced activation of MRs and GRs in motor control requires consideration in intervention strategies to improve performance in health and disease.

Long-term maternal separation differentially alters serum corticosterone levels and blood neutrophil activity in A/J and C57BL/6 mouse offspring

OBJECTIVES

In this work, we searched for maternal separation effects on serum corticosterone levels and blood neutrophil activity in adult male A/J and C57BL/6 mouse offspring.

METHODS

40 male A/J mice and 40 male C57BL/6 mice were divided within each strain into two groups. Mice in the maternal separation group were separated from their mothers (1 h/day) on postnatal days 0-13. Mice in the control group were left undisturbed. On postnatal day 45, blood was drawn from all mice and used to assess neutrophil activity by flow cytometry and serum corticosterone levels by radioimmunoassay.

RESULTS

The results showed that each mouse strain responded differently to maternal separation, but in both cases, serum corticosterone levels were affected. In both strains, adult mice that experienced maternal separation showed lower serum corticosterone levels than control mice. In relation to control mice kept together with their mothers, the levels of serum corticosterone were 72.7 and 36.36% lower in A/J and C57BL/6 mice submitted to maternal separation, respectively. The current findings showed that maternal separation increased neutrophil activity in mice after reaching adulthood. The observed effects, although in the same direction, differed between A/J and C57BL/6 mice. Maternal separation increased both the percentage and intensity of phagocytosis in C57BL/6 mice, but had no effects on A/J mice. Furthermore, maternal separation increased basal and propidium iodide-labeled Staphylococcus aureus-induced oxidative burst in A/J mice but did not affect oxidative burst in C57BL/6 mice. Finally, phorbol myristate acetate-induced oxidative burst increased in both strains.

CONCLUSION

These results indicate that early maternal separation increases innate immunity, most likely by modifying hypothalamus-pituitary-adrenal axis activity. This suggests that maternal separation is a good model for stress which produces long-term neuroimmune changes whatever the animal species and strain used.

Effects of individual housing on behavior and resistance to Ehrlich tumor growth in mice

This study analyzed in Balb/C mice the effects of individual housing on behavior, serum corticosterone and resistance to Ehrlich tumor growth. Mice (60 days old) were individually (IH) or grouped housed (G) (10-12 animals/cage) for 14-21 days. The 1st day of the housing condition was considered experimental day 1 (ED1). Results showed that on ED21, IH mice, when compared to G mice, presented no differences on corticosterone serum levels when kept undisturbed; however, an increased level of this hormone was observed in IH mice after an immobilization stress challenge. An increased time spent in the plus-maze closed arms and a decreased time in the open arms were also observed in IH mice. When compared to G animals, after inoculation with 10(5) Ehrlich tumor cells on ED1, IH mice presented an increase in volume of ascitic fluid and number of tumor cells. The survival time of IH mice was also shorter than that measured in G animals. Furthermore, IH mice injected with a different number of tumor cells on ED1 always presented increased Ehrlich tumor cells than G group. Interestingly, these effects were not observed when the tumor cells injection was done on ED4. These results suggest that individual-housing conditions induce an altered immune-endocrine response and, at the same time, decrease animals' resistance to Ehrlich tumor growth. It is proposed that the neural link between the behavioral and immunological changes observed after the stress of individual housing might involve the activation of the HPA axis.

Rapid non-genomic effects of glucocorticoids on oxidative stress in a guinea pig model of asthma

BACKGROUND AND OBJECTIVE

Glucocorticoids (GC) may exert therapeutic effects in asthma by a rapid non-genomic mechanism. The lungs of asthmatic patients are exposed to oxidative stress, which is believed to be critical in the pathogenesis of asthma. The aim of this study was to investigate whether GC exert a rapid non-genomic effect on oxidative stress in asthmatic guinea pigs.

METHODS

The guinea pig asthma model was used to assess inhibitory effects of budesonide (BUD) on oxidative stress. BAL fluid (BALF), trolox equivalent antioxidant capacity and lung manganese superoxide dismutase (MnSOD) activity were measured by spectrophotometry. Superoxide anion production was measured by cytochrome c reduction assay.

RESULTS

Oxidative stress occurred within minutes following antigen challenge and BUD reduced the severity of oxidative stress in asthmatic guinea pigs within 15 min. BUD significantly decreased BALF trolox equivalent antioxidant capacity and lung MnSOD activity, as compared with those of vehicle-treated asthmatic guinea pigs (P < 0.05). Additionally, BUD rapidly inhibited in vitro superoxide anion production by BALF cells and bronchi harvested from sensitized animals. These rapid effects were not blocked by the GC receptor antagonist RU486 and/or the protein synthesis inhibitor cycloheximide.

CONCLUSIONS

BUD reduced oxidative stress in a guinea pig model of asthma by a rapid non-genomic mechanism. These data suggest new mechanisms whereby GC treatments may benefit asthma.

Inhaled corticosteroids reduce asthma-associated airway hyperperfusion through genomic and nongenomic mechanisms

Inhaled corticosteroids have both genomic and nongenomic actions on the tracheobronchial (airway) vasculature in patients with bronchial asthma. Genomic actions involve the activation or repression of target genes associated with inflammation, and reduce inflammatory hyperperfusion in the airway. In contrast, nongenomic actions are mediated by rapid cellular mechanisms, and induce transient vasoconstriction. This article reviews recent progress on the mechanisms by which inhaled corticosteroids reverse inflammatory blood flow changes in the airway in asthma.