Chronic stress induces mast cell-dependent bacterial adherence and initiates mucosal inflammation in rat intestine

Epithelia under metabolic stress perceive commensal bacteria as a threat

The normal gut flora has been implicated in the pathophysiology of inflammatory bowel disease and there is increased interest in the role that stress can play in gut disease. The chemical stressor dinitrophenol (DNP, uncouples oxidative phosphorylation) was injected into the ileum of laparotomized rats and mitochondria structure, epithelial permeability, and inflammatory cell infiltrate were examined 6 and 24 hours later. Monolayers of human colonic epithelial cells (T84, HT-29) were treated with DNP +/- commensal Escherichia coli, followed by assessment of epithelial permeability, bacterial translocation, and chemokine (ie, interleukin-8) synthesis. Delivery of DNP into rat distal ileum resulted in disruption of epithelial mitochondria; similar changes were noted in mildly inflamed ileal resections from patients with Crohn's disease. Also, DNP-treated ileum displayed increased gut permeability and immune cell recruitment. Subsequent studies revealed deceased barrier function, increased bacterial translocation, increased production of interleukin-8, and enhanced mobilization of the transcription factor AP-1 in the model epithelial cell lines exposed to commensal bacteria (E. coli strains HB101 or C25), but only when the monolayers were pretreated with DNP (0.1 mmol/L). These data suggest that enteric epithelia under metabolic stress perceive a normally innocuous bacterium as threatening, resulting in loss of barrier function, increased penetration of bacteria into the mucosa, and increased chemokine synthesis. Such responses could precipitate an inflammatory episode and contribute to existing enteric inflammatory disorders.

Opposing effects of short- and long-term stress on airway inflammation

Between 20% and 35% of subjects with asthma experience asthma exacerbations during periods of stress. The biological mechanisms underlying these exacerbations are not clearly understood, and the role of psychologic factors in the pathophysiology of asthma remains controversial. We investigated the ability of psychologic stress to modulate airway inflammation and airway hyperresponsiveness (AHR) to methacholine in a murine model of asthma. Animals were exposed to a stressor daily for 3 (short-term stress) or 7 (long-term stress) days. After allergen challenge, AHR was assessed through plethysmography, and bronchoalveolar lavage cells were counted as a measure of inflammation. After short-term stress, inflammatory cell number was decreased compared with unstressed animals, whereas levels of interleukin (IL)-6, IL-9, and IL-13 were increased. Administration of a corticosteroid receptor antagonist, before stress, prevented the decrease in inflammatory cell numbers. In contrast, animals stressed for 7 consecutive days showed a significant increase in inflammatory cell numbers, which was independent of the glucocorticoid response, but no change in cytokine levels. AHR was not altered in stressed animals. Our results indicate that repeated exposure to stress over the long term engages different mechanisms than short-term stress and can exacerbate the chronic inflammatory responses of the airway.

Neuromodulation of enteropathogen internalization in Peyer's patches from porcine jejunum

Jejunal Peyer's patches (JPP) are innervated sites of immune induction and enteropathogen infection. We investigated the role of enteric nerves in modulating pathogen entry into porcine JPP. Presumptive norepinephrine (NE)-containing nerve fibers were localized in JPP domes and follicle-associated villi by secondary immunofluorescence histochemistry. NE or the neuronal conduction blocker saxitoxin increased intracellular internalization of pathogenic Salmonella choleraesuis and Escherichia coli O157:H7, but not nonpathogenic E. coli, into isolated JPP mucosa. NE action was prevented by the alpha-adrenergic antagonist phentolamine. Withdrawal of enteric neural activity or NE administration appears to modulate JPP interactions with pathogenic bacteria.

Inflammatory bowel disease and irritable bowel syndrome: separate or unified?

Both irritable bowel syndrome and inflammatory bowel diseases share symptoms of altered bowel habits associated with abdominal pain or discomfort. Irritable bowel syndrome has been referred to as a functional bowel disorder, which is diagnosed by a characteristic cluster of symptoms in the absence of detectable structural abnormalities. Inflammatory bowel disease is a heterogeneous group of disorders characterized by various forms of chronic mucosal and/or transmural inflammation of the intestine. In this review, the authors discuss recent evidence suggesting several potential mechanisms that might play a pathophysiologic role in both syndromes. Possible shared pathophysiologic mechanisms include altered mucosal permeability, an altered interaction of luminal flora with the mucosal immune system, persistent mucosal immune activation, alterations in gut motility, and a role of severe, sustained life stressors in symptom modulation. It is proposed that similarities and differences between the two syndromes can best be addressed within the framework of interactions between the central nervous system and the gut immune system. Based on recent reports of low-grade mucosal inflammation in subpopulations of patients meeting current diagnostic criteria for irritable bowel syndrome, therapeutic approaches shown to be effective in inflammatory bowel disease, such as probiotics, antibiotics, and antiinflammatory agents, have been suggested as possible therapies for certain patients with irritable bowel syndrome.

[Effectiveness of hyperbaric oxygenation as a factor of increasing the resistance of the human body to space flight conditions]

In four experimental runs (30 test subjects in 407 tests), the beneficial effect of hyperbaric oxygenation (HBO) on flight tolerance was demonstrated. HBO sessions (7-8 sessions of an hour in duration during 10-12 days at pO2 = 2 atm) helped subjects with poor altitude tolerance to increase the altitude ceiling by 1 km and reserve time at altitudes of 6-7 km by 3-4 min, the effect being persistent for 2-3 months. Statokinetic tolerance of subjects with medium motion sickness susceptibility grew by 2-2.5 times after the above HBO sessions. As compared to regular rest, the HBO treatment shortened two-fold the period of recovery of the health state and work capacity of operators, which went down during flight, and increased 15-20% the time of repeated work prior to failure in a stressful environment.