Author: BioactiveCompoundLibrary

In the BB rat model, the expression of CLDN1, one of the main sealing claudins of the intestine, was lower compared to controls at all investigated time points, also at 30 days when the permeability parameters were still similar in both strains. The reason for lower CLDN1 expression is unclear, but it may represent a genetic susceptibility. Our data are in partial agreement with Visser et al. who reported decreased CLDN1 expression in the ileum of 50 to 70 day old BB-DP rats, but not at 30–50 days. It is unclear whether regional variation, i.e. jejunum vs. ileum, or a different substrain may explain the difference in time of onset. A lower expression of CLDN1 has also been reported in one study in patients with diarrhea-predominant IBS, although not confirmed by others. Only from the age of 50 days, intestinal permeability increased in BB-DP animals, coinciding with an enhanced expression of CLDN2, a pore-forming claudin that enhances permeability. Combined, these data suggest that in our model lower expression of CLDN1 is insufficient to induce increased permeability and only the combination with increased CLDN2, of which the trigger has not been identified yet, leads to the barrier defect. Increased expression of CLDN2 has also been reported in intestinal biopsies of patients with IBD and IBS. However, the exact mechanisms by which the overexpression of CLDN2 can contribute to disease pathogenesis are still elusive since only small, supposedly non-immunogenic, solutes can permeate through CLDN2 pores. Intriguingly, the mucosal-toserosal flux of the 20 kDa dextran was unchanged at 50 days, while a clear decrease in TEER was present. At the later time points, a progressive rise in dextran passage was observed, in contrast to a stable difference in TEER. At least two different routes of intestinal paracellular flux have been reported in literature: a large-capacity pathway for small solutes and water, the ‘pore pathway’, and a small-capacity pathway for larger molecules, the ‘leak pathway’. The mucosal-toserosal flux of macromolecules is regulated by the leak pathway, while TEER reflects a combination of both pore and leak pathway. Although cross-talk exists to some extent, both pathways are regulated separately. Our data suggest that the pore pathway is affected first in BB-DP animals, while the defect in the leak pathway only follows at later time points. However, we cannot exclude that the size of the dextran used in our BI-D1870 experiments prevented us from detecting early differences in the leak pathway. The combination of different sizes of tracers could help to answer this question, which, however, was beyond the scope of the current study. The observed alterations in permeability and the fact that inflammation progresses over time from the mucosa to the muscle layer, point towards the involvement of a luminal factor. Previous studies have supported this hypothesis.

The first study demonstrated a low-grade lymphocytic myenteric ganglionitis in 9 out of 10 patients with severe IBS. More recently, the same group published a followup study showing a lymphocytic infiltrate in 48/65 patients with enteric dysmotility, a newly described FGID entity characterized by severe abdominal symptoms and dysmotility on small bowel manometry. It is unknown what proportion of patients with functional dyspepsia and IBS actually show enteric dysmotility and myenteric plexus abnormalities. Possible mechanisms of symptom generation in FGID include direct activation of sensory neurons by immune mediators, but also disturbed motility linked to alterations in the enteric nervous system. Research in animal models of postinflammatory dysmotility indicated a selective loss of inhibitory innervation. In keeping with this mechanism, we previously reported impaired gastric accommodation in postinfectious functional dyspepsia patients which was linked to an impaired nitrergic relaxation of the fundus. In the current study we confirmed an important reduction of nitrergic neurons in the jejunal myenteric plexus of older BB-rats with myenteric ganglionitis. This finding was confirmed functionally by a decreased nitrergic contribution to the EFS-induced relaxation of the longitudinal smooth muscle under NANC conditions. Recently, we have reported impaired gastric accommodation related to impaired nitrergic inhibition in the BB-DP rat. Additional studies investigating intestinal transit and visceral hypersensitivity are necessary to definitely confirm the BB-DP rat as a model for FGID. Also, it will be worthwhile to investigate whether sex-related differences and psychopathology traits such as anxiety, psychological stress and depression, similar to human FGID, can also be found in this rat model. A potential weakness of our study is the fact that only jejunum was studied, while most symptoms of IBS are thought to originate from the lower gastrointestinal tract. However, also in IBS patients, abnormalities in permeability and inflammation are present in the proximal small intestine. Moreover, we reported altered permeability and immune activation in the duodenum of patients with functional dyspepsia. Nevertheless, involvement of other segments of the gastrointestinal tract like the colon or the stomach needs to be studied in detail in follow-up studies in the BB-rat. In conclusion, we propose the BB-rat as a spontaneous animal model to study the pathogenesis of FGID. In the current study we describe the sequence of early impaired mucosal integrity leading to a GDC-0879 progressive, transmural inflammatory reaction, ultimately resulting in a myenteric ganglionitis with concomitant loss of nitrergic neurons and disturbed motility in the jejunum. These findings suggest an early pathogenic role for the impaired barrier function in the BB-rat model.

Over time of intestinal barrier function, mucosal and neuromuscular inflammation and loss of nitrergic motor neuron function in the normoglycemic BB-DP rat. We hypothesize that intestinal permeability is an early feature of the normoglycemic BB-DP rat, preceding inflammation and neuromuscular alterations, suggesting its disease-initiating role. In the current study we described the complex chain of events leading from early impaired mucosal integrity to myenteric BAY 73-4506 755037-03-7 ganglionitis and dysmotility in a spontaneous rat model of leaky gut. We demonstrated the presence of intestinal hyperpermeability prior to the development of mucosal immune activation in BB-DP rats, suggesting a disease-initiating role. At later time points, half of the animals developed a transmural inflammatory reaction with myenteric ganglionitis. Finally, in the older rats with intraganglionic inflammation, a loss of nitrergic neurons and function was observed. Our findings suggest that impaired mucosal integrity can give rise to a transmurally progressing inflammation resulting in disturbed motility, providing an insightful model for human FGID. Increased intestinal permeability and low-grade inflammatory alterations in the gastrointestinal tract have been suggested to contribute to the pathogenesis of FGID. A cascade in which intestinal permeability represents the first hit, leading to immune activation and subsequent neuromuscular alterations, is often proposed in the literature. However, because of the lack of drugs which can restore the leaky barrier and the fact that patients will only present themselves at the time of symptoms, it is challenging to separate cause from effect in humans. In the current study in BB-rats, we found an impaired barrier function in young rats of 50 days, a time point at which no immune cell infiltration or increased MPO-activity was observed. Furthermore, the expression of TNFa, IFNc, IL1b and IL13 was not increased in these young rats. This is of particular importance since it is well established that these cytokines can impair intestinal barrier function. We speculate that the initial defect in the intestinal barrier leads to the subepithelial penetration of unprocessed antigens, inciting an inflammatory reaction, which in turn maintains the permeability defect at the later time points. These events may lead to a vicious cycle as suggested by the correlation between the permeability and inflammatory parameters in the older animals and by the fact that the permeability parameters in the older animals without ganglionitis were comparable to controls. In order to definitely confirm this hypothesized biphasic permeability defect, experiments using anti-inflammatory treatments are warranted. The barrier function of the intestinal mucosa is regulated primarily by the apical junction complex, of which the tight junction is the most critical component.

This insight into HSP70-mediated NK cell activation may lead to the development of new therapeutic approaches that use NK cells to target cancer or virus-infected cells. Functional gastrointestinal disorders like irritable bowel syndrome and functional dyspepsia are characterized by bothersome gastrointestinal complaints in the absence of an underlying organic cause that readily explains the symptoms. Despite the high prevalence, the pathophysiology of FGID remains incompletely understood and the current XAV939 treatment options are limited and have suboptimal efficacy. Impaired intestinal barrier function, low-grade immune activation, and altered neuronal control of gastrointestinal motility, have been suggested to be involved in the pathogenesis. An attractive and often-cited disease model for FGID, and also for chronic inflammatory bowel disease, is based on luminal antigen penetration through an impaired intestinal barrier leading to immune activation in the intestinal wall. On the other hand, it is well recognized that increased intestinal permeability may also be a consequence of inflammatory changes. The current data on intestinal permeability in human intestinal disorders are mainly associative, with a possible exception of Crohn’s disease, and celiac disease. Especially in FGID, a causeconsequence relationship between the observed alterations in permeability, immune activation and motility disturbances, has not been established so far and is subject of ongoing debate. The distinction is relevant since therapeutic interventions aimed at restoring barrier function could represent a novel treatment approach to several gastrointestinal disorders. A spontaneous animal model sharing key intestinal characteristics of human FGID would be instrumental to separate cause from consequence and to study future treatments. The BioBreeding rat is a well-established animal model for type 1 diabetes. The BB-rat consists of two strains, the diabetesresistant and the diabetes-prone strain. Hyperglycemia develops in 50–95% of the BB-DP animals depending on the substrain, diet and housing conditions. The hyperglycemic BB-DP rat displays increased intestinal permeability prior to the development of diabetes, mucosal and neuromuscular inflammation and loss of nitrergic motor neuron function. We have previously reported that the development of the inflammatory enteropathy and loss of nitrergic neurons in the BB-rat also occur in BB-DP animals which do not develop diabetes. These features potentially identify the normoglycemic BB-DP rat as a suitable animal model for inflammatory neuromuscular dysfunction. However, current data on intestinal permeability and functional neuromuscular data are limited to diabetic animals, in which diabetes potentially is a confounding factor. Moreover, it is unclear how permeability, inflammation and intestinal nitrergic neuropathy.

Injury to the lung when viewed on histopathology, nor is there a significant increase in cells recruited to the alveoli when measured in bronchoalveolar lavage fluid at 24 hours. The in vitro macrophage data suggests the administered agmatine may have stimulated the resident cells of the lung without inducing a measurable recruitment of neutrophils. In an attempt to replicate the co-stimulatory conditions of the cell culture experiments we intratracheally injected both LPS and agmatine into the lungs of mice. However the inflammatory response over the lungs alone was difficult to measure given the robust systemic response to LPS in the liver and abdomen. Using a similar NF-kB reporter mouse we administered both LPS and agmatine via the intraperitoneal route and measured the total body NF-kB response in this model. At 4 hours agmatine augments the LPS induced NF-kB response, but this response is more rapidly diminished by 8 hours. As with the cellular response, the systemic response to agmatine and LPS in an animal model is likely complex, however it is clear that agmatine administration does augment the inflammatory response in vitro and in vivo when exogenously administered. With advances in analytical techniques, the ability to track multiple small molecules in diverse matrices has led to a heightened appreciation of the complicated chemical mediators of both immune cell and bacterial signaling. Frequently these signaling molecules, such as cytokines and quorum sensing molecules, are unique to a species, having the presumed intent of communicating a very specific message to neighboring cells. Occasionally a pathogen may adapt a way to intercept or destroy cell signaling molecules with potential benefit to bacterial survival. This work on the arginine decarboxylase pathways of mammals and bacteria was spawned by the observation that the benign molecule agmatine induces select P. aeruginosa strains to form a biofilm. Agmatine has no deleterious effect on P. aeruginosa up to millimolar quantities, and is readily metabolized to putrescine which can be a source of ATP production after conversion to alanine or succinate. While many of the cues that coerce a pathogen to form a biofilm are not known, most are thought to be cues of environmental stress. This suggests that agmatine may be a cue of stress to P. aeruginosa in one of its natural environments. Agmatine has not been described in the human lung until now. Its role in human biology is poorly understood having only recently been shown to exist in mammals. It has known receptor affinities for a2-adrenoreceptors, serotonin, and SB203580 imidazoline receptors, and has been shown to be a direct inhibitor to NOS-2 presumably given its similarity to the NOS substrate arginine. It is not known how important agmatine is in most organ systems, or if its receptor actions are evolutionarily intended or merely a consequence of similarity to the known ligands of each of those receptors.