Restraint stress-induced elevation of endogenous glucocorticoids decreases Peyer's patch cell numbers via mechanisms that are either dependent or independent on apoptotic cell death

Protective Effects of Inulin on Stress-Recurrent Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a chronic inflammatory condition of the digestive tract and is closely associated with the homeostasis of the gut microbiota. Inulin, as a natural prebiotic, displays anti-inflammatory activity and maintains equilibrium of the intestinal microbiota. In this study, our research aimed to explore the potential of inulin in enhancing intestinal immunity and reducing inflammation in stress-recurrent IBD. In this study, a co-culture intestinal epithelium model and a stress-recurrent IBD mouse model was used to examine the protective effects of inulin. It was observed that inulin digesta significantly reduced pro-inflammatory cytokine expression (CXCL8/IL8 and TNFA) and increased MUC2 expression in intestinal epithelial cells. In vivo, our findings showed that Inulin intake significantly prevented IBD symptoms. This was substantiated by a decrease in serum inflammatory markers (IL-6, CALP) and a downregulation of inflammatory cytokine (Il6) in colon samples. Additionally, inulin intake led to an increase in short-chain fatty acids (SCFAs) in cecal contents and a reduction in the expression of endoplasmic reticulum (ER) stress markers (CHOP, BiP). Our results highlight that inulin can improve stress-recurrent IBD symptoms by modulating microbiota composition, reducing inflammation, and alleviating ER stress. These findings suggested the therapeutic potential of inulin as a dietary intervention for ameliorating stress-recurrent IBD.

Intestinal Homeostasis under Stress Siege

Intestinal homeostasis encompasses a complex and balanced interplay among a wide array of components that collaborate to maintain gut barrier integrity. The appropriate function of the gut barrier requires the mucus layer, a sticky cushion of mucopolysaccharides that overlays the epithelial cell surface. Mucus plays a critical anti-inflammatory role by preventing direct contact between luminal microbiota and the surface of the epithelial cell monolayer. Moreover, mucus is enriched with pivotal effectors of intestinal immunity, such as immunoglobulin A (IgA). A fragile and delicate equilibrium that supports proper barrier function can be disturbed by stress. The impact of stress upon intestinal homeostasis results from neuroendocrine mediators of the brain-gut axis (BGA), which comprises a nervous branch that includes the enteric nervous system (ENS) and the sympathetic and parasympathetic nervous systems, as well as an endocrine branch of the hypothalamic-pituitary-adrenal axis. This review is the first to discuss the experimental animal models that address the impact of stress on components of intestinal homeostasis, with special emphasis on intestinal mucus and IgA. Basic knowledge from animal models provides the foundations of pharmacologic and immunological interventions to control disturbances associated with conditions that are exacerbated by emotional stress, such as irritable bowel syndrome.

Protective effects of Colomast®, A New Formulation of Adelmidrol and Sodium Hyaluronate, in A Mouse Model of Acute Restraint Stress

Stress is generally defined as a homeostatic disruption from actual or implied threats and alters the homeostatic balance of different body organs, such as gastrointestinal function and the hypothalamic-pituitary-adrenal axis (HPA), inducing the release of glucocorticoid hormones. Stress is also known to be a risk factor for the development of depression and anxiety. However, until today there are no suitable therapies for treating of stress. The aim of this study was to explore the protective effect of Colomast®, a new preparation containing Adelmidrol, an enhancer of physiological of palmitoylethanolamide (PEA), and sodium hyaluronate in an animal model of immobilization stress. Acute restraint stress (ARS) was induced in mice by fixation for 2 h of the four extremities with an adhesive tape and Colomast® (20 mg/kg) was administered by oral gavage 30 min before the immobilization. Colomast® pre-treatment was able to decrease histopathological changes in the gastrointestinal tract, cytokines expression, neutrophil infiltration, mast cell activation, oxidative stress, as well as modulate nuclear factor NF-kB and apoptosis pathways after ARS induction. Moreover, Colomast® was able to restore tight junction in both ileum and hippocampus and cortex. Additionally, we demonstrated that Colomast® ameliorated depression and anxiety-related behaviours, and modulate inflammatory and apoptosis pathways also in brain after ARS induction. In conclusion, our results suggest Colomast® to be a potential approach to ARS.

Intermittent fasting promotes bacterial clearance and intestinal IgA production in Salmonella typhimurium-infected mice

The impact of intermittent fasting versus ad libitum feeding during Salmonella typhimurium infection was evaluated in terms of duodenum IgA levels, bacterial clearance and intestinal and extra-intestinal infection susceptibility. Mice that were intermittently fasted for 12 weeks or fed ad libitum were infected with S. typhimurium and assessed at 7 and 14 days post-infection. Next, we evaluated bacterial load in the faeces, Peyer's patches, spleen and liver by plate counting, as well as total and specific intestinal IgA and plasmatic corticosterone levels (by immunoenzymatic assay) and lamina propria IgA levels in plasma cells (by cytofluorometry). Polymeric immunoglobulin receptor, α- and J-chains, Pax-5 factor, pro-inflammatory cytokine (tumour necrosis factor-α and interferon-γ) and anti-inflammatory cytokine (transforming growth factor-β) mRNA levels were assessed in mucosal and liver samples (by real-time PCR). Compared with the infected ad libitum mice, the intermittently fasted infected animals had (1) lower intestinal and systemic bacterial loads; (2) higher SIgA and IgA plasma cell levels; (3) higher mRNA expression of most intestinal parameters; and (4) increased or decreased corticosterone levels on day 7 and 14 post-infection, respectively. No contribution of liver IgA was observed at the intestinal level. Apparently, the changes following metabolic stress induced by intermittent fasting during food deprivation days increased the resistance to S. typhimurium infection by triggering intestinal IgA production and presumably, pathogen elimination by phagocytic inflammatory cells.

Citalopram protects against cold-restraint stress-induced activation of brain-derived neurotrophic factor and expression of nuclear factor kappa-light-chain-enhancer of activated B cells in rats

The present study evaluates the protective effect of citalopram against cold-restraint stress (CRS) paradigm. Rats were pretreated with citalopram (0.1, 1.0, and 10.0 mg/kg) acutely and repeatedly for 21 days before exposure to the CRS procedure. None of the doses of citalopram attenuated CRS-induced gastric ulcers in the acute study. In contrast, repeated pretreatment of citalopram at a dose level of 0.1 mg/kg attenuated the CRS-induced gastric ulcers. Citalopram (0.1 mg/kg) diminished CRS-induced increase in plasma corticosterone, but not plasma norepinephrine level in the chronic study indicating its effect on hypothalamic-pituitary-adrenal axis function. Repeated citalopram (0.1 mg/kg) pretreatment attenuated CRS-induced changes in serotonin turnover in the hippocampus and amygdala. Moreover, repeated pretreatment with citalopram (0.1 mg/kg) mitigated the CRS-induced increase in the expression of brain-derived neurotrophic factor (BDNF) and nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB) in the hippocampus and amygdala. These results suggest that there is a region- and a dose-specific effect of citalopram on CRS-induced BDNF-NFκB activation. Therefore, citalopram showed antistress activity in the CRS model through changes in the stress-responsive pathways such as hypothalamic-pituitary-adrenal-axis and brain serotonergic system apart from decreasing the expression of BDNF and NFκB.

Stress modulates intestinal secretory immunoglobulin A

Stress is a response of the central nervous system to environmental stimuli perceived as a threat to homeostasis. The stress response triggers the generation of neurotransmitters and hormones from the hypothalamus pituitary adrenal axis, sympathetic axis and brain gut axis, and in this way modulates the intestinal immune system. The effects of psychological stress on intestinal immunity have been investigated mostly with the restraint/immobilization rodent model, resulting in an up or down modulation of SIgA levels depending on the intensity and time of exposure to stress. SIgA is a protein complex formed by dimeric (dIgA) or polymeric IgA (pIgA) and the secretory component (SC), a peptide derived from the polymeric immunoglobulin receptor (pIgR). The latter receptor is a transmembrane protein expressed on the basolateral side of gut epithelial cells, where it uptakes dIgA or pIgA released by plasma cells in the lamina propria. As a result, the IgA-pIgR complex is formed and transported by vesicles to the apical side of epithelial cells. pIgR is then cleaved to release SIgA into the luminal secretions of gut. Down modulation of SIgA associated with stress can have negative repercussions on intestinal function and integrity. This can take the form of increased adhesion of pathogenic agents to the intestinal epithelium and/or an altered balance of inflammation leading to greater intestinal permeability. Most studies on the molecular and biochemical mechanisms involved in the stress response have focused on systemic immunity. The present review analyzes the impact of stress (mostly by restraint/immobilization, but also with mention of other models) on the generation of SIgA, pIgR and other humoral and cellular components involved in the intestinal immune response. Insights into these mechanisms could lead to better therapies for protecting against pathogenic agents and avoiding epithelial tissue damage by modulating intestinal inflammation.

Effects of restraint stress on NALT structure and nasal IgA levels

The effects of stress on the mucosal immune responses in inflammatory disorders of the gut, as well as on salivary and intestinal IgA levels are well known. However, its effects on the structure and function of the NALT have not yet been reported, and are examined in the present study. Balb/c mice were submitted to restraint stress for 3h per day during 4 or 8d. The immunohistochemistry and flow cytometric analysis revealed that repeated restraint stress (4 and 8d) decreased the percentage, compared to the control group, of CD3(+) and CD4(+) T cells, without affecting the percentage of CD8(+) T cells or B220(+) cells (B cells). The numbers of IELs (CD4(+) and CD8(+) T cells) were lower at 4d of stress and higher at 8d. IgA(+) cells in NALT and nasal IgA levels showed a similar pattern, being significantly lower at 4d of stress and significantly higher at 8d. In summary, repeated restraint stress altered the distribution and number of lymphocytes and IgA(+) cells in nasal mucosa, probably due to changes in norepinephrine and corticosterone levels.

Effect of repeated restraint stress on the levels of intestinal IgA in mice

The effects of restraint stress on the intestinal humoral immune system, particularly those about intestinal IgA production, have not been explored in detail. Thus, the purpose of this study was to assess the effect of restraint stress on the production and secretion of intestinal IgA as well as on the number of IgA+ cells in the intestinal lamina propria. The involvement of glucocorticoids and catecholamines were also evaluated. Mice were exposed to 1 or 4 h restraint stress for 4 d. The intestinal IgA concentration was quantified by ELISA and the number of IgA containing cells in the lamina propria was determined by immunohistochemistry. The effects of restraint were also analyzed in mice submitted to different procedures: adrenalectomy, chemical sympathectomy, treatment with a glucocorticoid antagonist (RU486), dexamethasone and epinephrine. The main findings were that (1) chronic restraint-stress reduced the intestinal IgA concentration without changing the number of IgA+ cells in lamina propria; (2) adrenalectomy restored the production of IgA in stressed mice; (3) RU486 and chemical sympathectomy partially blocked the decrease in intestinal IgA in stressed mice; and (4) pharmacological doses of dexamethasone and epinephrine significantly reduced the intestinal IgA concentration and the number of IgA+ cells. The restraint stress probably reduced the intestinal IgA concentration through the effects of glucocorticoids and catecholamines.

Effects of chronic stress on the immune response to oral human serum albumin-conjugated starch microparticles in rats

Uptake of antigens and bacteria over the follicle-associated epithelium (FAE) is increased after chronic psychological stress. We investigated whether stress affects the immune response to particle-conjugated antigens taken up via the FAE. Rats were submitted to two 10-day periods of water avoidance stress and orally immunized during these periods. Stressed immunized rats displayed altered cell populations and a Th1-skewed immune response within the lymphoid follicles, together with enhanced delayed-type hypersensitivity. We conclude that chronic stress affects the cell-mediated immune response after oral immunization, which may have implications for the understanding of allergic and autoimmune diseases and development of oral vaccines.

Mouse thymocyte apoptosis and cell loss in response to exercise and antioxidant administration

Various physical and psychological stressors can cause thymocyte apoptosis and cell loss in rodents. Although glucocorticoids (GC) are commonly implicated, oxidative stress may also play a role. The purpose of this study was to examine the effect of an acute bout of strenuous treadmill running, and the antioxidant N-acetyl-L-cysteine (NAC) on thymocyte loss and apoptosis. Eighty-eight female C57BL/6 mice were given NAC (1 g/kg, i.p.) or saline (SAL) 30 min before 90 min of treadmill exercise at a 2 degrees slope (EX; 30 min at 22 m/min; 30 min at 25 m/min; and 30 min at 28 m/min) and sacrificed immediately (Imm) or 24 h following EX. Control mice (NonEX) were exposed to treadmill noise and vibration without running. Thymocytes were isolated and analyzed for phosphatidylserine (PS) externalization (Annexin V), loss of membrane integrity, mitochondria membrane depolarization, intracellular hydrogen peroxide (H(2)O(2)) production, and intracellular glutathione (GSH) as well as protein levels of caspase 3, Bcl-2, and cytosolic cytochrome c. Blood was analyzed for corticosterone (CORT) concentrations by radioimmunoassay. Exercise stress caused a significant increase in plasma CORT concentrations in EX + SAL + Imm and EX + NAC + Imm groups compared to NonEX mice. Relative to NonEX mice, thymocytes isolated from EX + SAL + Imm mice showed signs of an early apoptotic profile as indicated by decreased GSH stores and increased mitochondrial membrane depolarization. These effects were followed by a 50% reduction in thymocyte numbers 24 h post-exercise (EX + SAL + 24 h). Alterations in GSH levels, mitochondrial membrane depolarization, and thymocyte loss were not observed in mice receiving NAC. These results suggest that exercise-induced thymocyte apoptosis and cell loss may be mediated via an oxidative stress pathway.

Intraepithelial but not lamina propria lymphocytes in the porcine gut are affected by dexamethasone treatment

It is well established that glucocorticoids are key regulators of the immune system and act as immunosuppressive agents in high concentrations. In the pig, effects on the gut immune system and trafficking of lymphocytes between tissues and blood plasma were not investigated so far. Twelve pigs of 70 kg were fed 0.4 mg portions of dexamethasone (Dexa) twice daily for 9 days or remained untreated (controls) and were sacrificed for tissue collection at the end of Dexa treatment. Another six pigs with jugular vein catheters were left untreated for 7 days (control period) and then received Dexa for 9 days. Blood was drawn twice during the control period and at days 3, 6 and 9 of the Dexa period for characterization of peripheral blood leukocytes. Cells were obtained from thymus, mesenteric lymph nodes, jejunal mucosa and Peyer's patches. Lymphoid cells from gut tissue were isolated from two fractions: the EDTA-fraction, containing the intraepithelial lymphocytes (IEL), and the Collagenase-fraction, containing the lamina propria lymphocytes (LPL). In all samples, cell counts and phenotypic characterization of cells by flow cytometry (FCM) were performed. In thymus, Dexa led to a more than 90% reduction of the absolute cell number, which was mainly found in the CD4+CD8+ subpopulation. Dexa effects on lymphocytes from mesenteric lymph nodes were less severe (50%) and led mainly to a decrease (71%) of B-lymphocytes. The number of lymphocytes in the EDTA-fraction (IEL) of the jejunal mucosa decreased significantly by 56% in the Dexa-treated animals compared to the controls, whereas the number of lymphocytes in the Collagenase-fraction (LPL) decreased only moderately. In the Peyer's patches, a decreasing tendency in the number of lymphocytes in the EDTA-fraction was observed which, however, was not significant. In blood, monocytes and granulocytes were significantly increased in an order of 60%. The data show that supraphysiological amounts of Dexa remarkably reduce cell numbers in thymus and also in the intraepithelial compartment of the jejunal mucosa and ileal Peyer's patches. In blood, a notable homeostasis was observed for several leukocyte populations whereas both monocytes and granulocytes increased.

Adrenalectomy in mice does not prevent loss of intestinal lymphocytes after exercise

Exhaustive exercise is associated with an increase in circulating glucocorticoids (GCs), lymphocyte apoptosis, and a reduction in intestinal lymphocyte number. The present study examined the role of GCs on the numerical changes seen in intestinal lymphocytes after exercise. Female C57BL/6 mice were bilaterally adrenalectomized (ADX; n = 18) or given sham surgery (Sham; n = 18) and assigned to one of three exercise conditions: treadmill running (28 m/min, 90 min, 2 degrees slope) and killed immediately or after 24 h recovery, or not exercised and killed immediately after 90-min exposure to the treadmill environment. Lymphocytes were isolated from the intestines with CD45(+) cells collected by positive selection using magnetic bead separation columns, and lymphocyte subpopulations were analyzed by flow cytometry for CD45(+), CD3alphabeta(+), CD3gammadelta(+), CD8beta(+), CD8alpha(+), CD4(+), and NK(+) phenotypic markers. ADX mice had significantly more intestinal CD45(+) leukocytes (P < 0.05) and CD3alphabeta(+) (P < 0.05), CD3gammadelta(+) (P < 0.01), CD8alpha(+) (P < 0.001), and NK(+) (P < 0.05) intestinal lymphocytes than Sham mice. There was a significant effect of exercise condition on total intestinal CD45(+) leukocytes (P < 0.01) and CD3alphabeta(+) (P < 0.05), CD8alpha(+) (P < 0.001), and CD4(+) (P < 0.05) intestinal lymphocytes, with fewer cells at 24 h postexercise compared with the other treatment conditions. There were no surgical x exercise interaction effects on the CD3 and CD8 phenotype numbers. Plasma corticosterone was virtually nil in ADX mice regardless of exercise condition but was significantly elevated in Sham mice immediately postexercise (P < 0.001). The data indicate that ADX does not prevent the loss of lymphocytes from the intestinal mucosa 24 h after strenuous exercise and GCs are not directly causal in the leukopenia of exercise.

Electric foot shock stress-induced exacerbation of alpha-galactosylceramide-triggered apoptosis in mouse liver

Recently, liver natural killer T (NKT) cells, which are specifically stimulated by alpha-galactosylceramide (alpha-GalCer), were found to play a critical role in intrahepatic immunity to several infections and certain hepatic disorders. However, the role of psychophysical stress on NKT cell-dependent liver injury induced by alpha-GalCer still remains to be elucidated. In this study, we employed inescapable electric foot shock as the mode of psychophysical stress and evaluated its effect on alpha-GalCer-induced hepatitis. Pre-exposure of 12 hours of foot shock stress before alpha-GalCer administration significantly enhanced alpha-GalCer-triggered increase in serum alanine aminotransferase levels, followed by increases in both liver caspase-3 activity and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL)-positive hepatocytes, thus indicating that the liver NKT cell-dependent apoptotic response was exacerbated by stress. Foot shock stress also significantly increased both the number of liver NKT cells and Fas expression levels on hepatocytes. Pretreatment with RU-486, a glucocorticoid (GC) receptor antagonist, completely reversed such stress-induced enhancement of the alpha-GalCer-triggered serum alanine aminotransferase and hepatocyte Fas antigen responses. In contrast, such a reversal effect was not found in the mice pretreated with naloxone, a micro-opioid receptor antagonist, which thus suggests that an elevation of endogenous GCs, but not beta-endorphin, as responsible for such stress-induced aggravation in mouse hepatitis models. In conclusion, foot shock stress-induced elevation of endogenous GCs exacerbates alpha-GalCer-initiated hepatic apoptosis through the expansion of liver NKT cells and the up-regulation of hepatocyte Fas antigen.

Endogenous glucocorticoids inhibit scratching behavior induced by the administration of compound 48/80 in mice

In this study, we investigated the effects of endogenous glucocorticoids on the compound 48/80 (a condensation product of N-methyl-p-methoxyphenethylamine with formaldehyde)-induced mouse scratching behavior using either RU-486 (mifepristone), a glucocorticoid receptor antagonist, or a surgical resection of the adrenal glands. Subcutaneous injection of compound 48/80 induced not only a corticosterone elevation in the plasma but also an enhanced expression of corticotropin releasing hormone (CRH) mRNA in the paraventricular nucleus, which thus suggests that hypothalamic-pituitary-adrenal axis is activated by the compound 48/80-induced cutaneous reaction. Inhibition of such an endogenous glucocorticoid activity by RU-486 significantly increased the degree of scratching behavior at not only the early-phase (<60 min) but also the late-phase (>60 min) time course after the injection of compound 48/80. Since the elevation of the histamine levels in the plasma in the RU-486-treated mice was no longer found in late-phase scratching behavior, these results thus indicate that histamine is a dominant mediator responsible for early-phase scratching behavior, while different mediators other than histamine may be also involved in the induction of late-phase scratching behavior. Moreover, surgical removal of adrenal glands also significantly increased the compound 48/80-induced scratching behavior without affecting anxiety and locomotor parameters, indicating that endogenous glucocorticoids exert their anti-pururitogenic effects independently of changes in behavioral performance. In conclusion, endogenous glucocorticoid activity was found to suppress the compound 48/80-induced scratching behavior in mice.