Colonic hyperalgesia triggered by proteinase-activated receptor-2 in mice: involvement of endogenous bradykinin

Intracolonic (i.col.) administration of the PAR2-activating peptide (PAR2AP) SLIGRL-NH2 slowly develops visceral hypersensitivity to i.col. capsaicin in ddY mice. Thus, we further analyzed roles of PAR2 in colonic hypersensitivity, using the novel potent PAR2AP, 2-furoyl-LIGRL-NH2 and PAR2-knockout (KO) mice. In ddY mice, i.col. 2-furoyl-LIGRL-NH2 produced delayed (6 h later) facilitation of capsaicin-evoked visceral nociception, an effect being much more potent than SLIGRL-NH2. Such effects were mimicked by i.col. trypsin. In wild-type (WT), but not PAR2-KO, mice of C57BL/6 background, i.col. PAR2 agonists caused delayed facilitation of sensitivity to capsaicin. The PAR2-triggered visceral hypersensitivity was abolished by a bradykinin B2 receptor antagonist, HOE-140. Our data thus provide ultimate evidence for role of PAR2 in colonic hypersensitivity, and suggest involvement of the bradykinin-B2 pathway.