Pneumonia as a long-term consequence of chronic psychological stress in BALB/c mice

Long-Term Stress and Concomitant Marijuana Smoke Exposure Affect Physiology, Behavior and Adult Hippocampal Neurogenesis

Marijuana is a widely used recreational drug with increasing legalization worldwide for medical purposes. Most experimental studies use either synthetic or plant-derived cannabinoids to investigate the effect of cannabinoids on anxiety and cognitive functions. The aim of this study was to mimic real life situations where young people smoke cannabis regularly to relax from everyday stress. Therefore, we exposed young adult male NMRI mice to daily stress and concomitant marijuana smoke for 2 months and investigated the consequences on physiology, behavior and adult hippocampal neurogenesis. Animals were restrained for 6-h/day for 5-days a week. During the stress, mice were exposed to cannabis smoke for 2 × 30 min/day. We burned 2 “joints” (2 × 0.8 g marijuana) per occasion in a whole body smoking chamber. Cannabinoid content of the smoke and urine samples was measured by HPLC and SFC-MS/MS. Body weight gain was recorded daily and we did unrestrained, whole body plethysmography to investigate pulmonary functions. The cognitive performance of the animals was evaluated by the novel object recognition and Y maze tests. Anxietyrelated spontaneous locomotor activity and self-grooming were assessed in the open field test (OFT). Adult neurogenesis was quantified post mortem in the hippocampal dentate gyrus. The proliferative activity of the precursor cells was detected by the use of the exogenous marker 5-bromo-20-deoxyuridine. Treatment effects on maturing neurons were studied by the examination of doublecortin-positive neurons. Both stress and cannabis exposure significantly reduced body weight gain. Cannabis smoke had no effect on pulmonary functions, but stress delayed the maturation of several lung functions. Neither stress, nor cannabis smoke affected the cognitive functioning of the animals. Results of the OFT revealed that cannabis had a mild anxiolytic effect and markedly increased self-grooming behavior. Stress blocked cell proliferation in the dentate gyrus, but cannabis had no effect on this parameter. Marijuana smoke however had a pronounced impact on doublecortin-positive neurons influencing their number, morphology and migration. In summary, we report here that long-term stress in combination with cannabis smoke exposure can alter several health-related measures, but the present experimental design could not reveal any interaction between these two treatment factors except for body weight gain.

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 .

Overcrowding stress decreases macrophage activity and increases Salmonella Enteritidis invasion in broiler chickens

Overcrowding stress is a reality in the poultry industry. Chickens exposed to long-term stressful situations present a reduction of welfare and immunosuppression. We designed this experiment to analyse the effects from overcrowding stress of 16 birds/m(2) on performance parameters, serum corticosterone levels, the relative weight of the bursa of Fabricius, plasma IgA and IgG levels, intestinal integrity, macrophage activity and experimental Salmonella Enteritidis invasion. The results of this study indicate that overcrowding stress decreased performance parameters, induced enteritis and decreased macrophage activity and the relative bursa weight in broiler chickens. When the chickens were similarly stressed and infected with Salmonella Enteritidis, there was an increase in feed conversion and a decrease in plasma IgG levels in the stressed and Salmonella-infected birds. We observed moderate enteritis throughout the duodenum of chickens stressed and infected with Salmonella. The overcrowding stress decreased the macrophage phagocytosis intensity and increased Salmonella Enteritidis counts in the livers of birds challenged with the pathogenic bacterium. Overcrowding stress via the hypothalamic-pituitary-adrenal axis that is associated with an increase in corticosterone and enteritis might influence the quality of the intestinal immune barrier and the integrity of the small intestine. This effect allowed pathogenic bacteria to migrate through the intestinal mucosa, resulting in inflammatory infiltration and decreased nutrient absorption. The data strengthen the hypothesis that control of the welfare of chickens and avoidance of stress from overcrowding in poultry production are relevant factors for the maintenance of intestinal integrity, performance and decreased susceptibility to Salmonella infection.

Acute heat stress impairs performance parameters and induces mild intestinal enteritis in broiler chickens: role of acute hypothalamic-pituitary-adrenal axis activation

Studies on the environmental consequences of stress are relevant for economic and animal welfare reasons. We recently reported that long-term heat stressors (31 ± 1°C and 36 ± 1°C for 10 h/d) applied to broiler chickens (Gallus gallus domesticus) from d 35 to 42 of life increased serum corticosterone concentrations, decreased performance variables and the macrophage oxidative burst, and produced mild, multifocal acute enteritis. Being cognizant of the relevance of acute heat stress on tropical and subtropical poultry production, we designed the current experiment to analyze, from a neuroimmune perspective, the effects of an acute heat stress (31 ± 1°C for 10 h on d 35 of life) on serum corticosterone, performance variables, intestinal histology, and peritoneal macrophage activity in chickens. We demonstrated that the acute heat stress increased serum corticosterone concentrations and mortality and decreased food intake, BW gain, and feed conversion (P < 0.05). We did not find changes in the relative weights of the spleen, thymus, and bursa of Fabricius (P > 0.05). Increases in the basal and the Staphylococcus aureus-induced macrophage oxidative bursts and a decrease in the percentage of macrophages performing phagocytosis were also observed. Finally, mild, multifocal acute enteritis, characterized by the increased presence of lymphocytes and plasmocytes within the lamina propria of the jejunum, was also observed. We found that the stress-induced hypothalamic-pituitary-adrenal axis activation was responsible for the negative effects observed on chicken performance and immune function as well as for the changes in the intestinal mucosa. The data presented here corroborate with those presented in other studies in the field of neuroimmunomodulation and open new avenues for the improvement of broiler chicken welfare and production performance.

Depression and incident lower limb amputations in veterans with diabetes

PROBLEM

Depression is associated with a higher risk of macrovascular and microvascular complications and mortality in diabetes, but whether depression is linked to an increased risk of incident amputations is unknown. We examined the association between diagnosed depression and incident non-traumatic lower limb amputations in veterans with diabetes.

METHODS

This was a retrospective cohort study from 2000-2004 that included 531,973 veterans from the Diabetes Epidemiology Cohorts, a national Veterans Affairs (VA) registry with VA and Medicare data. Depression was defined by diagnostic codes or antidepressant prescriptions. Amputations were defined by diagnostic and procedural codes. We determined the HR and 95% CI for incident non-traumatic lower limb amputation by major (transtibial and above) and minor (ankle and below) subtypes, comparing veterans with and without diagnosed depression and adjusting for demographics, health care utilization, diabetes severity and comorbid medical and mental health conditions.

RESULTS

Over a mean 4.1 years of follow-up, there were 1289 major and 2541 minor amputations. Diagnosed depression was associated with an adjusted HR of 1.33 (95% CI: 1.15-1.55) for major amputations. There was no statistically significant association between depression and minor amputations (adjusted HR 1.01, 95% CI: 0.90-1.13).

CONCLUSIONS

Diagnosed depression is associated with a 33% higher risk of incident major lower limb amputation in veterans with diabetes. Further study is needed to understand this relationship and to determine whether depression screening and treatment in patients with diabetes could decrease amputation rates.

Psychological stress-induced, IDO1-dependent tryptophan catabolism: implications on immunosuppression in mice and humans

It is increasingly recognized that psychological stress influences inflammatory responses and mood. Here, we investigated whether psychological stress (combined acoustic and restraint stress) activates the tryptophan (Trp) catabolizing enzyme indoleamine 2,3-dioxygenase 1(IDO1) and thereby alters the immune homeostasis and behavior in mice. We measured IDO1 mRNA expression and plasma levels of Trp catabolites after a single 2-h stress session and in repeatedly stressed (4.5-days stress, 2-h twice a day) naïve BALB/c mice. A role of cytokines in acute stress-induced IDO1 activation was studied after IFNγ and TNFα blockade and in IDO1^−/− mice. RU486 and 1-Methyl-L-tryptophan (1-MT) were used to study role of glucocorticoids and IDO1 on Trp depletion in altering the immune and behavioral response in repeatedly stressed animals. Clinical relevance was addressed by analyzing IDO1 activity in patients expecting abdominal surgery. Acute stress increased the IDO1 mRNA expression in brain, lung, spleen and Peyer's patches (max. 14.1±4.9-fold in brain 6-h after stress) and resulted in a transient depletion of Trp (−25.2±6.6%) and serotonin (−27.3±4.6%) from the plasma measured 6-h after stress while kynurenine levels increased 6-h later (11.2±9.3%). IDO1 mRNA up-regulation was blocked by anti-TNFα and anti-IFNγ treatment. Continuous IDO1 blockade by 1-MT but not RU486 treatment normalized the anti-bacterial defense and attenuated increased IL-10 inducibility in splenocytes after repeated stress as it reduced the loss of body weight and behavioral alterations. Moreover, kynurenic acid which remained increased in 1-MT treated repeatedly stressed mice was identified to reduce the TNFα inducibility of splenocytes in vitro and in vivo. Thus, psychological stress stimulates cytokine-driven IDO1 activation and Trp depletion which seems to have a central role for developing stress-induced immunosuppression and behavioral alteration. Since patients showed Trp catabolism already prior to surgery, IDO is also a possible target enzyme for humans modulating immune homeostasis and mood.

Antimicrobial anxiety: the impact of stress on antimicrobial immunity

Leukocytes and epithelial cells are fundamental to antimicrobial immunity. Their antimicrobial responses are an evolutionarily conserved component of the innate immune system and are influenced by the host's response to external stimuli. The efficacy of host defense via antimicrobial responses derives from the ability of AMPs to rapidly identify and eradicate foreign microbes and activate proinflammatory pathways, and from the capacity of later innate and adaptive immune responses to amplify protection through distinct biochemical mechanisms. Recent advances in neuroimmunology have identified a direct link between the neuroendocrine and immune systems, where environmental stimuli are generally believed to promote a transient effect on the immune system in response to environmental challenges and are presumably brought back to baseline levels via neuroendocrine pathways. Stress is an environmental stimulus that flares from a variety of circumstances and has become engrained in human society. Small bouts of stress are believed to enhance the host's immune response; however, prolonged periods of stress can be detrimental through excess production of neuroendocrine-derived mediators that dampen immune responses to invasive pathogens. Elucidation of the mechanisms behind stress-induced immune modulation of antimicrobial responses will ultimately lead to the development of more effective therapeutic interventions for pathologic conditions. It is the intent of this review to broaden the existing paradigm of how stress-related molecules dampen immune responses through suppression of antimicrobial mechanisms, and to emphasize that bacteria can use these factors to enhance microbial pathogenesis during stress.

Different stress-related phenotypes of BALB/c mice from in-house or vendor: alterations of the sympathetic and HPA axis responsiveness

Background

Laboratory routine procedures such as handling, injection, gavage or transportation are stressful events which may influence physiological parameters of laboratory animals and may interfere with the interpretation of the experimental results. Here, we investigated if female BALB/c mice derived from in-house breeding and BALB/c mice from a vendor which were shipped during their juvenile life differ in their HPA axis activity and stress responsiveness in adulthood.

Results

We show that already transferring the home cage to another room is a stressful event which causes an increased HPA axis activation for at least 24 hours as well as a loss of circulating lymphocytes which normalizes during a few days after transportation. However and important for the interpretation of experimental data, commercially available strain-, age- and gender-matched animals that were shipped over-night showed elevated glucocorticoid levels for up to three weeks after shipment, indicating a heightened HPA axis activation and they gained less body weight during adolescence. Four weeks after shipment, these vendor-derived mice showed increased corticosterone levels at 45-min after intraperitoneal ACTH challenge but, unexpectedly, no acute stress-induced glucocorticoid release. Surprisingly, activation of monoaminergic pathways were identified to inhibit the central nervous HPA axis activation in the vendor-derived, shipped animals since depletion of monoamines by reserpine treatment could restore the stress-induced HPA axis response during acute stress.

Conclusions

In-house bred and vendor-derived BALB/c mice show a different stress-induced HPA axis response in adulthood which seems to be associated with different central monoaminergic pathway activity. The stress of shipment itself and/or differences in raising conditions, therefore, can cause the development of different stress response phenotypes which needs to be taken into account when interpreting experimental data.

Psychological stress increases expression of IL-10 and its homolog IL-19 via beta-adrenoceptor activation: reversal by the anxiolytic chlordiazepoxide

Recent studies from our laboratory indicate that psychological stress is a potent inducer of the anti-inflammatory cytokine interleukin (IL)-10, raising the possibility that the IL-10 family of cytokines may be key mediators of stress-induced immunosuppression. In this study we examined the impact of psychological stress (restraint stress) on expression of IL-10, and the novel IL-10 family members IL-19, IL-20 and IL-24 in mouse spleen following an in vivo challenge with lipopolysaccharide (LPS). We found that stressor exposure significantly augmented LPS-induced IL-10 expression. Similarly, IL-19 expression was induced by LPS, and this was significantly enhanced by restraint stress. In contrast, expression of IL-24 was not significantly altered by LPS or stress, and expression of IL-20 was largely not detectable in vivo in either saline or LPS-treated animals. Consistent with a role for sympathetic nervous system (SNS) activation in stress-induced immune regulation, the sympathetic neurotransmitter noradrenaline increased LPS-induced IL-10 and IL-19 expression in splenocytes and dendritic cells, and the ability of noradrenaline to induce expression of these cytokines was blocked by pre-treatment with the beta-adrenoceptor antagonist propranolol. Similarly, pre-treatment of mice with the peripherally acting beta-adrenoceptor antagonist nadolol completely blocked the stress-induced increase in IL-10 and IL-19 mRNA expression. Finally, pre-treatment with the benzodiazepine anxiolytic chlordiazepoxide prevented the stress-induced increase in IL-10 and IL-19 expression. Taken together, these data demonstrate that psychological stress induces expression of the IL-10 and its homolog IL-19 via activation of beta-adrenoceptors, and the ability of stress to induce these cytokines is prevented by treatment with the anxiolytic chlordiazepoxide. The findings suggest that stress enhances the production of immunosuppressive cytokines, which may impact on stress-related disease processes.