Activation of proteinase-activated receptor-1 inhibits neurally evoked chloride secretion in the mouse colon in vitro.
The proteinase-activated thrombin receptor-1 (PAR-1) belongs to a unique family of G protein-coupled receptors activated by proteolytic cleavage. We studied the effect of PAR-1 activation in the regulation of ion transport in mouse colon in vitro. Expression of PAR-1 in mouse colon was assessed by RT-PCR and immunohistochemistry. To study the role of PAR-1 activation in chloride secretion, mouse colon was mounted in Ussing chambers. Changes in short-circuit current (Isc) were measured in tissues exposed to either thrombin, saline, the PAR-1-activating peptide TFLLR-NH2, or the inactive reverse peptide RLLFT-NH2, before electrical field stimulation (EFS). Experiments were repeated in the presence of either a PAR-1 antagonist or in PAR-1-deficient mice to assess receptor specificity. In addition, studies were conducted in the presence of chloride-free buffer or the muscarinic antagonist atropine to assess chloride dependency and the role of cholinergic neurons in the PAR-1-induced effect. PAR-1 mRNA was expressed in full-thickness specimens and mucosal scrapings of mouse colon. PAR-1 immunoreactivity was found on epithelial cells and on neurons in submucosal ganglia where it was colocalized with both VIP and neuropeptide Y. After PAR-1 activation by thrombin or TFLLR-NH2, secretory responses to EFS but not those to forskolin or carbachol were significantly reduced. The reduction in the response to EFS was not observed in the presence of the PAR-1 antagonist, in PAR-1-deficient mice, when chloride was excluded from the bathing medium, or when atropine was present. PAR-1 is expressed in submucosal ganglia in the mouse colon and its activation leads to a decrease in neurally evoked epithelial chloride secretion.
Buresi
Michelle C
MC
Mucosal Inflammation Research Group, University of Calgary, Calgary, Alberta, Canada.
Vergnolle
Nathalie
N
Sharkey
Keith A
KA
Keenan
Catherine M
CM
Andrade-Gordon
Patricia
P
Cirino
Giuseppe
G
Cirillo
Donatella
D
Hollenberg
Morley D
MD
MacNaughton
Wallace K
WK
D000818:Animals; D002712:Chlorides / Q000378:metabolism*; D003106:Colon / Q000737:chemistry / Q000294:innervation / Q000502:physiology*; D015870:Gene Expression; D066298:In Vitro Techniques; D007413:Intestinal Mucosa / Q000737:chemistry / Q000378:metabolism*; D017136:Ion Transport; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009478:Neuropeptide Y / Q000032:analysis; D012333:RNA, Messenger / Q000032:analysis; D044463:Receptor, PAR-1 / Q000032:analysis / Q000502:physiology*; D015398:Signal Transduction; D014660:Vasoactive Intestinal Peptide / Q000032:analysis
D002712:Chlorides; D009478:Neuropeptide Y; D012333:RNA, Messenger; D044463:Receptor, PAR-1; D014660:Vasoactive Intestinal Peptide