Corticotropin-Releasing Hormone Receptor 2-Deficient Mice Have Reduced Intestinal Inflammatory Responses

Abstract

Corticotropin-releasing hormone (CRH) and urocortins (Ucn) bind with various affinities to two G-protein-coupled receptors, CRHR1 and CRHR2, which are expressed in brain and in peripheral tissues, including immune cells. CRHR2-deficient mice display anxiety-like behavior, hypersensitivity to stress, altered feeding behavior and metabolism, and cardiovascular abnormalities. However, the phenotype of these mice in inflammatory responses has not been determined. In the present study we found that compared with wild-type CRHR2-null mice developed substantially reduced intestinal inflammation and had lower intestinal mRNA expression of the potent chemoattractants keratinocyte chemokine and monocyte chemoattractant protein 1 following intraluminal exposure to Clostridium difficile toxin A, a potent enterotoxin that mediates antibiotic-associated diarrhea and colitis in humans. This effect was recapitulated by administration of astressin 2B, a selective CRHR2 antagonist, before toxin A exposure. Moreover, Ab array analysis revealed reduced expression of several inflammatory chemokines, including keratinocyte chemokine and monocyte chemoattractant protein 1 in toxin A-exposed mice pretreated with astressin 2B. Real-time RT-PCR of wild-type mouse intestine showed that only UcnII, but not other Ucn, was significantly up-regulated by ileal administration of toxin A at 4 h compared with buffer exposure. We also found that human colonic epithelial HT-29 cells express CRHR2α mRNA, whereas expression of β and γ spliced variants was minimal. Moreover, treatment of HT-29 cells with UcnII, which binds exclusively to CRHR2, stimulated expression of IL-8 and monocyte chemoattractant protein 1. Taken together, these results provide direct evidence that CRHR2 mediates intestinal inflammatory responses via release of proinflammatory mediators at the colonocyte level.

Melanin-concentrating hormone as a mediator of intestinal inflammation

“…Our previous studies on the role of additional neuropeptides such as substance P, neurotensin, and members of the corticotropinreleasing hormone (CRH) family of peptides in intestinal inflammation demonstrated that receptors for these molecules are expressed in intestinal epithelial cells and their expression is increased during the course of inflammation (30)(31)(32)(33)(34). Hence, to examine epithelial cell expression of MCH and its receptors, we used a laser capture microdissection (LCM) approach to isolate colonic epithelial cells from cryopreserved surgical specimens obtained from patients with IBD and controls (35).…”

Role of Corticotropin-releasing Factor in Gastrointestinal Permeability

“…26,27 Central release of CRF and urocortins mediates autonomic, hormonal, and behavioural responses to stress and at the gastrointestinal tract, stimulates the enteric nervous system to modulate gastrointestinal motility and secretion. [28][29][30] In addition, immune cells, regional sensory and sympathetic nerves, enterochromaffin cells, and enteric cells release CRF and urocortins within the gastrointestinal tract 28 to modulate mucosal function and gastrointestinal motility. 29 Different type of stress, acute or chronic, physical or psycho-logical, have been shown to influence properties of the intestinal barrier function, including ion and water secretion, intestinal permeability, mucus secretion, and also intestinal flora in both human and animal models.…”

Multi-facets of Corticotropin-releasing Factor in Modulating Inflammation and Angiogenesis

“…19 Moreover, enterotoxin-induced ileitis was reduced in CRF 2 receptor-deficient mice or the CRF 2 receptor specific antagonist astressin 2-B -treated mice along with decreased mRNA expression levels of keratinocyte chemokine and monocyte chemoattractant protein 1. 15 Additionally, CRF 2 receptor activation by Ucn2 treatment was able to stimulate the expression of IL-8 and monocyte chemoattractant protein 1 in human colonic epithelial HT-29 cells expressing CRF 2 receptor. 15 In line with this, RNA interference of CRF 2 receptor but not CRF 1 receptor dramatically reduced the extent of ulceration during colitis.…”

“…15 Additionally, CRF 2 receptor activation by Ucn2 treatment was able to stimulate the expression of IL-8 and monocyte chemoattractant protein 1 in human colonic epithelial HT-29 cells expressing CRF 2 receptor. 15 In line with this, RNA interference of CRF 2 receptor but not CRF 1 receptor dramatically reduced the extent of ulceration during colitis. 20 It is noteworthy that the expression of the CRF family and its receptor was altered in the inflammatory tissue.…”

“…Inflammatory bowel disease (IBD), chronic or acute intestinal inflammatory condition caused by aberrant immune response to gut microflora in genetically susceptible individuals, is the most intensively studied inflammatory conditions, as it is related to the immune modulatory role of the CRF family. [13][14][15] Interestingly, the CRF family members can be pro-inflammatory or anti-inflammatory depending on the inflammatory settings and their opposing effect on inflammation appears to result from their implication in angiogenesis. Such dual effects on inflammatory responses can be fulfilled by interleukin (IL)-8 and vascular endothelial growth factor (VEGF) which are potent angiogenic factors.…”