Regulation of the Pacemaker Activity of Colonic Interstitial Cells of Cajal by Protease-Activated Receptors: Involvement of Hyperpolarization-Activated Cyclic Nucleotide Channels.
OBJECTIVE
The exact mechanism of protease-activated receptors (PARs) on pacemaker activity of interstitial cells of Cajal (ICCs) has not been reported. We investigated the effects on pacemaker activity by the activation of PARs and its signal mechanisms in colonic ICCs.


METHODS
The whole-cell patch-clamp technique, RT-PCR and Ca2+ imaging were used in cultured ICCs from mouse colon.


RESULTS
PAR-1 and PAR-2 were expressed in Ano-1 positive ICCs. TFLLR-NH2 (a PAR-1 agonist) and trypsin (a PAR-2 agonist) depolarized the membrane and increased the pacemaker potential frequency. U-73122 (a phospholipase C (PLC) inhibitor) and thapsigargin (a Ca2+ ATPase inhibitor) suppressed the TFLLR-NH2- and trypsin-induced effects on pacemaker potential. TFLLR-NH2 and trypsin also increased intracellular Ca2+ ([Ca2+]i) intensity with increasing of Ca2+ oscillations. Genistein (a tyrosine kinase inhibitor), SP600125 (a JNK inhibitor), CsCl, ZD7288, clonidine (hyperpolarization-activated cyclic nucleotide (HCN) channel blockers), SQ-22536 and dideoxyadenosine (adenylate cyclase inhibitors) suppressed the increased pacemaker potential frequency without effects on depolarization of the membrane induced by TFLLR-NH2 and trypsin.


CONCLUSIONS
These results suggest that activation of PAR-1 and PAR-2 modulates the pacemaker activity of colonic ICCs through the PLC-dependent [Ca2+]i release pathway. The increased pacemaker potential frequency by PAR-1 and PAR-2 was also dependent on tyrosine kinase, JNK, and HCN activation.
Departments of Physiology, College of Medicine, Chosun University, Gwangju, Korea.
Dong Hoon
DH
Shin
Man Woo
MW
Kim
Seok
S
Choi
Dong Chuan
DC
Zuo
Chan Guk
CG
Park
Young Dae
YD
Kim
Jun
J
Lee
Ju Yeon
JY
Cho
Insuk
I
So
Jae Yeoul
JY
Jun
D000818:Animals; D003106:Colon / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D005260:Female; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels / Q000502:physiology*; D056885:Interstitial Cells of Cajal / Q000187:drug effects / Q000502:physiology*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D009842:Oligopeptides / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D044463:Receptor, PAR-1 / Q000819:agonists / Q000378:metabolism*; D044464:Receptor, PAR-2 / Q000819:agonists / Q000378:metabolism*; D044462:Receptors, Proteinase-Activated / Q000378:metabolism
D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D009842:Oligopeptides; C462999:PAR-1-activating peptide; D044463:Receptor, PAR-1; D044464:Receptor, PAR-2; D044462:Receptors, Proteinase-Activated