Gut fungi in irritable bowel syndrome: A painful recognition

This thesis focused on the role of fungi in the irritable bowel syndrome (IBS). IBS is a common, stress related, functional gastrointestinal disorder, characterized by chronic abdominal pain. A part of IBS patients show increased perception of pain to a rectal stimulus compared to healthy subjects. This so called hypersensitivity of the viscera is thought to represent a pathological mechanism behind the abdominal pain characteristic for IBS. The relevance of fungi was studied in the pre-clinical rat maternal separation model. In this model, rat pups are predisposed by maternal separation, and subjection to acute stress at adult age triggers, similar to IBS patients, hypersensitivity of the viscera. We observed that treatment with antifungals prevented the development of post stress visceral hypersensitivity. Remarkably, this hypersensitive phenotype in IBS model rats was accompanied by a specific fungal signature. Probably the development visceral hypersensitivity involves the recognition of fungal cell wall β-glucans by Dectine-1, a pathogen recognition receptor expressed on mast cells. After Dectine-1 activation, mast cells respond by the release of histamine which ultimately results in sensitization of afferent neurons. There is no current treatment for abdominal pain in IBS. Our research has identified a completely novel mechanism by which IBS develops and might thus lead to novel therapies

Gut fungi in irritable bowel syndrome: A painful recognition

This thesis focused on the role of fungi in the irritable bowel syndrome (IBS). IBS is a common, stress related, functional gastrointestinal disorder, characterized by chronic abdominal pain. A part of IBS patients show increased perception of pain to a rectal stimulus compared to healthy subjects. This so called hypersensitivity of the viscera is thought to represent a pathological mechanism behind the abdominal pain characteristic for IBS. The relevance of fungi was studied in the pre-clinical rat maternal separation model. In this model, rat pups are predisposed by maternal separation, and subjection to acute stress at adult age triggers, similar to IBS patients, hypersensitivity of the viscera. We observed that treatment with antifungals prevented the development of post stress visceral hypersensitivity. Remarkably, this hypersensitive phenotype in IBS model rats was accompanied by a specific fungal signature. Probably the development visceral hypersensitivity involves the recognition of fungal cell wall β-glucans by Dectine-1, a pathogen recognition receptor expressed on mast cells. After Dectine-1 activation, mast cells respond by the release of histamine which ultimately results in sensitization of afferent neurons. There is no current treatment for abdominal pain in IBS. Our research has identified a completely novel mechanism by which IBS develops and might thus lead to novel therapies. Les

Gut fungi in irritable bowel syndrome:A painful recognition

This thesis focused on the role of fungi in the irritable bowel syndrome (IBS). IBS is a common, stress related, functional gastrointestinal disorder, characterized by chronic abdominal pain. A part of IBS patients show increased perception of pain to a rectal stimulus compared to healthy subjects. This so called hypersensitivity of the viscera is thought to represent a pathological mechanism behind the abdominal pain characteristic for IBS. The relevance of fungi was studied in the pre-clinical rat maternal separation model. In this model, rat pups are predisposed by maternal separation, and subjection to acute stress at adult age triggers, similar to IBS patients, hypersensitivity of the viscera. We observed that treatment with antifungals prevented the development of post stress visceral hypersensitivity. Remarkably, this hypersensitive phenotype in IBS model rats was accompanied by a specific fungal signature. Probably the development visceral hypersensitivity involves the recognition of fungal cell wall β-glucans by Dectine-1, a pathogen recognition receptor expressed on mast cells. After Dectine-1 activation, mast cells respond by the release of histamine which ultimately results in sensitization of afferent neurons. There is no current treatment for abdominal pain in IBS. Our research has identified a completely novel mechanism by which IBS develops and might thus lead to novel therapies

Absence of diurnal variation in visceromotor response to colorectal distention in normal Long Evans rats

BACKGROUND: Enhanced colorectal sensitivity (i.e. visceral hypersensitivity) is thought to be a pathophysiological mechanism in irritable bowel syndrome (IBS). In healthy men a circadian variation in rectal perception to colonic distention was described. Disturbed day and night rhythms, which occur in shift work and trans meridian flights, are associated with the prevalence of IBS. This raises the question whether disruptions of circadian control are responsible for the observed pathology in IBS. Prior to investigating altered rhythmicity in relation to visceral hypersensitivity in a rat model for IBS, it is relevant to establish whether normal rats display circadian variation similar to healthy men. METHODOLOGY AND FINDINGS: In rodents colorectal distension leads to reproducible contractions of abdominal musculature. We used quantification of this so called visceromotor response (VMR) by electromyography (EMG) to assess visceral sensitivity in rats. We assessed the VMR in normal male Long Evans rats at different time points of the light/dark cycle. Although a control experiment with male maternal separated rats confirmed that intentionally inflicted (i.e. stress induced) changes in VMR can be detected, normal male Long Evans rats showed no variation in VMR along the light/dark cycle in response to colorectal distension. CONCLUSIONS: In the absence of a daily rhythm of colorectal sensitivity in normal control rats it is not possible to investigate possible aberrancies in our rat model for IBS

Painful interactions: Microbial compounds and visceral pain

Visceral pain, characterized by abdominal discomfort, originates from organs in the abdominal cavity and is a characteristic symptom in patients suffering from irritable bowel syndrome, vulvodynia or interstitial cystitis. Most organs in which visceral pain originates are in contact with the external milieu and continuously exposed to microbes. In order to maintain homeostasis and prevent infections, the immune- and nervous system in these organs cooperate to sense and eliminate (harmful) microbes. Recognition of microbial components or products by receptors expressed on cells from the immune and nervous system can activate immune responses but may also cause pain. We review the microbial compounds and their receptors that could be involved in visceral pain development

A novel, high stringency selection system allows screening of few clones for high protein expression.

To obtain highly productive mammalian cell lines, often large numbers of clones need to be screened. This is largely due to low selection stringencies, creating many, but low protein producing clones. To remedy this problem, a novel, very stringent selection system was designed, to create few, but high protein producing clones. In essence, a selection marker with a startcodon that confers attenuated translation initiation frequency was placed upstream of the gene of interest with a startcodon that confers optimal translation initiation. From the transcribed bicistronic mRNA, the selection marker is translated at a low frequency, and the protein of interest at a high frequency. This selection system is so stringent that clones form only rarely. However, application of anti-repressor elements, which increase promoter activity, did induce the formation of clones that expressed proteins at high levels. When combined with anti-repressor elements, this novel selection system can be a valuable tool to rapidly create few, but highly productive mammalian cell lines