ABSTRACT
Irritable bowel syndrome (IBS) is one of the most prevalent functional disorders in Chile impacting on socio-economic development due to significantly impaired quality of life of the individual. It is characterised by abdominal discomfort associated with alterations in bowel habit and increased visceral hypersensitivity. One of the outstanding features of IBS is the presence of a bi-directional imbalance of gut-brain interactions, which can induce alterations in the intestinal immune response. IBS is characterised by increased intestinal mast cell activity associated with alterations of para-cellular permeability and activation of sensory nerve endings. The increased proximity of mast cell to colonic nerves is correlated with abdominal pain and increased visceral hypersensitivity of the patients. In spite of the well-described role of mast cell in the induction of mucosal inflammation, in IBS only a low-grade inflammation is observed. The present review discuses the possible immune-regulatory mechanisms that are involved in IBS pathophysiology.
El síndrome de intestino irritable (SII) es considerado uno de los trastornos funcionales más prevalente en Chile, que impacta el desarrollo socio-económico del país debido al deterioro de la calidad de vida de los individuos que lo portan. Es caracterizado por molestias abdominales asociadas a alteraciones en el hábito de defecación e hipersensibilidad visceral. Una de las características más destacadas en el SII es la presencia de un desequilibrio de las interacciones en el eje intestino-cerebro, el cual puede inducir alteraciones en la respuesta inmune intestinal. El SII es caracterizado por una aumentada actividad de los mastocitos en el intestino, asociada con alteraciones en la permeabilidad para-celular epitelial y la activación de terminaciones nerviosas en la mucosa intestinal. El aumento de la cercanía de los mastocitos a nervios colónicos está relacionado con el dolor abdominal y la hipersensibilidad visceral de los pacientes. Pese a que está muy bien descrito el papel del mastocito en la inducción de la inflamación en mucosas, en el SII se observa sólo un bajo-grado de inflamación. En la presente revisión se discute los posibles mecanismos regulatorios inmunes que están involucrados en la fisiopatología del SII.
Subject(s)
Humans , Irritable Bowel Syndrome/physiopathology , Irritable Bowel Syndrome/immunology , Colon/innervation , Hypersensitivity , Inflammation , Mast Cells/pathology , Nervous System/physiopathologyABSTRACT
The pathophysiology of irritable bowel syndrome [IBS] remains elusive. In countries where enteric parasitic infection is common, its role in the development of IBS is controversial. Parasites induce the Th2 immune response that elaborates cytokines such as interleukin [IL]-5, which causes eosinophilia. Eosinophilic cationic protein [ECP] is one of the mediators released during the activation of eosinophils. This study aims to determine the relationship between symptoms suggestive of IBS and parasitic infection in IBS patients and to evaluate the serum levels of IL-5, ECP and eosinophilic count as potentially useful serological tests in those patients. Thirty-five IBS patients fulfilling Rome II criteria with absence of intestinal helminthic infection by direct smear method and no history of associated allergic conditions were studied. Ten healthy controls were included. Microscopic examination of stools for intestinal parasites, eosinophilic count and erythrocyte sedimentation rate were done. Colonoscopy was performed to rule out inflammatory bowel changes. Serum levels of IL-5 and ECP were measured. Intestinal parasitic infection was present in 37% [13/35] of IBS patients vs. 20% [2/10] in controls. Of the 35 IBS patients, 13 [37%] had protozoal infection. Mean eosinophilic count, IL-5 level and ECP were significantly higher in IBS patients than in controls. Eosinophilic count and ECP serum level were significantly high in IBS patients with parasitic infection. A significant number of patients with symptoms suggestive of IBS demonstrated evidence of parasitic infection in their stool samples. The IL-5 serum level, eosinophilic count and ECP serum level might be useful tests for detecting parasitic infection aetiology in IBS patients after exclusion of conditions inducing the Th2 response. Larger case-controlled studies are required to clearly define the parasitic pathophysiology in IBS