Role Of Crff2 Receptors In Colonic Ion Secretion In Response To Stress-Related Peptides

Background and Aims Stress increases intestinal secretion and exacerbates symptoms of irritable bowel syndrome (IBS). Peripherally-derived corticotropin-releasing factor (CRF) is known to mediate stress-induced intestinal secretion, presumably by activation of CRF1 receptors in the gut. The present study aimed to ascertain the role of CRF2 activation in intestinal secretion by three other members of CRF peptide family, urocortin (UCN) 1-3, in wild-type (WT) and CRF2 knockout (Crhr2-/-) mice. Methods Mucosal/submucosal preparations from proximal colon of WT and Crhr2-/- mice of adult male mice were mounted in Ussing chambers for measurement of short-circuit current (Isc) as an indicator of ion secretion. Results The colonic mucosa/submucosa preparations were exposed to different concentrations of UCN1, 2, or 3 (30 nM, 100 nM, 300 nM, and 1 mM) on the basolateral side. All three UCNs evoked increases in colonic ISC (ΔISC) in a dose-dependent manner. The EC50s were 392.64nM for UCN1, 103.28nM for UCN2, and 231.21nM for UCN3. Application of CRF or stressin1 (a selective CRF1 receptor agonist) (30nM – 1mM) also caused increases in ISC with an EC50 of 597.04nM or 588.84nM, respectively. The potency order was therefore UCN2 > UCN3 > UCN1 > stressin1 » CRF. At each concentration tested, UCN3 produced significantly greater ΔISC responses than that caused by stressin1, CRF, UCN1, or UCN2. Involvement of the CRF receptor subtypes in UCN1-3 evoked ΔISC responses was investigated with the selective CRF1 receptor antagonist NBI27914 and the selective CRF2 receptor antagonist antisauvagine-30. Both NBI27914 and antisauvagine-30 significantly suppressed UCN1 (300nM)-induced ΔISC responses (p < 0.05). The ΔISC responses evoked by UCN2 (100nM) and UCN3 (100nM) were significantly suppressed by antisauvagine-30 (p < 0.05 and p < 0.0001, respectively), but were not influenced by NBI27914 (p > 0.05). In the Crhr2-/- mice, UCN2 (1mM) failed to evoke any ΔISC compared with WT controls (p < 0.01). UCN3 (1mM)-evoked ΔISC responses were significantly decreased by 57.21% in the Crhr2-/- mice compared with WT mice (p < 0.05). In contrast, stressin1 (1mM)-evoked ΔISC response did not differ between WT and Crhr2-/- mice (p > 0.05). Conclusions UCN1-3 all caused an increase of colonic ion secretion, which mimicked the effects of stress and CRF. UCN1-induced increase of colonic ion secretion was mediated by both CRF1 and CRF2, whereas UCN2 and UCN3-induced increase of colonic ion secretion was mediated only by CRF2. Since UCN2 and UCN3 have greater potency and efficacy on colonic ion secretion compared with UCN1, CRF, and stressin1, it is logical to conclude that CRF2 receptors played a predominant role in the pro-secretory effects of UCNs.