Will corticosteroids and other anti-inflammatory agents be effective for diarrhea-predominant irritable bowel syndrome?

High altitude exposures and intestinal barrier dysfunction

Gastrointestinal complaints are often reported during ascents to high altitude (> 2500 m), though their etiology is not known. One potential explanation is injury to the intestinal barrier which has been implicated in the pathophysiology of several diseases. High altitude exposures can reduce splanchnic perfusion and blood oxygen levels causing hypoxic and oxidative stress. These stressors might injure the intestinal barrier leading to consequences such as bacterial translocation and local/systemic inflammatory responses. The purpose of this mini review is to 1) discuss the impact of high-altitude exposures on intestinal barrier dysfunction, and 2) present medications and dietary supplements which may have relevant impacts on the intestinal barrier during high-altitude exposures. There is a small but growing body of evidence which shows that acute exposures to high altitudes can damage the intestinal barrier. Initial data also suggests that prolonged hypoxic exposures can compromise the intestinal barrier through alterations in immunological function, microbiota, or mucosal layers. Exertion may worsen high-altitude related intestinal injury via additional reductions in splanchnic circulation and greater hypoxemia. Collectively these responses can result in increased intestinal permeability and bacterial translocation causing local and systemic inflammation. More research is needed to determine the impact of various medications and dietary supplements on the intestinal barrier during high-altitude exposures.

Irritable bowel syndrome: an integrated explanatory model for clinical practice

BACKGROUND

Although irritable bowel syndrome (IBS) is a symptom-based diagnosis, clinicians' management of and communication about the disorder is often hampered by an unclear conceptual understanding of the nature of the problem. We aimed to elucidate an integrated explanatory model (EM) for IBS from the existing literature for pragmatic use in the clinical setting.

METHODS

Systematic and exploratory literature searches were performed in PubMed to identify publications on IBS and EMs.

KEY RESULTS

The searches did not identify a single, integrated EM for IBS. However, three main hypotheses were elucidated that could provide components with which to develop an IBS EM: (i) altered peripheral regulation of gut function (including sensory and secretory mechanisms); (ii) altered brain-gut signaling (including visceral hypersensitivity); and (iii) psychological distress. Genetic polymorphisms and epigenetic changes may, to some degree, underlie the etiology and pathophysiology of IBS and could increase the susceptibility to developing the disorder. The three model components also fit into one integrated explanation for abdominal symptoms and changes in stool habit. Additionally, IBS may share a common pathophysiological mechanism with other associated functional syndromes.

CONCLUSIONS & INFERENCES

It was possible to elucidate an integrated, three-component EM as a basis for clinicians to conceptualize the nature of IBS, with the potential to contribute to better diagnosis and management, and dialog with sufferers.

Antinociceptive effect of VSL#3 on visceral hypersensitivity in a rat model of irritable bowel syndrome: a possible action through nitric oxide pathway and enhance barrier function

Irritable bowel syndrome (IBS) is a functional bowel disorder characterized by visceral hypersensitivity and altered bowel function. There are increasing evidences suggested that VSL#3 probiotics therapy has been recognized as an effective method to relieve IBS-induced symptoms. The aim of this study was to examine the effects of VSL#3 probiotics on visceral hypersensitivity (VH), nitric oxide (NO), fecal character, colonic epithelium permeability, and tight junction protein expression. IBS model was induced by intracolonic instillation of 4% acetic acid and restraint stress in rats. After subsidence of inflammation on the seventh experimental day, the rats were subjected to rectal distension, and then the abdominal withdrawal reflex and the number of fecal output were measured, respectively. Also, colonic permeability to Evans blue was measured in vivo, and tight junction protein expression was studied by immunohistochemistry and immunoblotting method. Rats had been pretreated with VSL#3 or aminoguanidine (NOS inhibitor) or VSL#3+ aminoguanidine before measurements. The rats at placebo group showed hypersensitive response to rectal distension (P < 0.05) and defecated more stools than control rats (P < 0.05), whereas VSL#3 treatment significantly attenuated VH and effectively reduced defecation. Aminoguanidine reduced the protective effects of VSL#3 on VH. A pronounced increase in epithelial permeability and decreased expression of tight junction proteins (occludin, ZO-1) in placebo group were prevented by VSL#3, but not aminoguanidine. VSL#3 treatment reduce the hypersensitivity, defecation, colonic permeability and increase the expression of tight junction proteins (occludin, ZO-1). As the part of this effect was lowered by NOS inhibitor, NO might play a role in the protective effect of VSL#3 to some extent.

Antinociceptive effect of chronic lithium on visceral hypersensitivity in a rat model of diarrhea-predominant irritable bowel syndrome: The role of nitric oxide pathway

BACKGROUND AND AIM

Lithium, a widely used drug in bipolar-affective disorders, plays gastro-protective roles. The effects of lithium on several tissues are mediated through nitric oxide (NO), which regulates gastrointestinal motility and mucosal integrity. The aim of this study was to investigate the protective effect of chronic lithium administration on visceral hypersensitivity and to investigate the role of NO as a potential mechanism of lithium in a rat model of irritable bowel syndrome.

METHODS

Colitis was induced by the intracolonic administration of acetic acid. After subsidence of inflammation on the seventh experimental day, nociception and defecation parameters were measured. A subgroup of animals had been pretreated with lithium carbonate (600 mg/L) for 35 days. Thereafter, either a non-selective NO synthase (NOS) inhibitor (N-nitro-L-arginine methyl ester [L-NAME], 10 mg/kg), a selective NOS inhibitor (aminoguanidine, 100 mg/kg), or saline were administered intraperitoneally 1 h before measurements.

RESULTS

Chronic lithium attenuated the visceral hypersensitivity, increased the nociceptive threshold, and decreased stool frequency. L-NAME and aminoguanidine decreased the nociceptive threshold and reduced the protective effects of lithium on visceral hypersensitivity. Stool frequency was increased in both the lithium-treated and water-treated groups by L-NAME administration, but not aminoguanidine. The form of defecation in the lithium-treated rats shifted toward hard stools rather than being soft and formless, but NOS inhibitors did not change the stool consistency pattern.

CONCLUSION

The results indicate the antinociceptive property of chronic lithium on visceral hypersensitivity. As this effect was lowered by NOS inhibitors, NO might play a role in the protective effect of lithium to some extent.