title: Restoration of uridine 5'-triphosphate-suppressed delayed rectifying K+currents by an NO activator KMUP-1 involves RhoA/Rho kinase signaling in pulmonary artery smooth muscle cells.
abstract: We have demonstrated that KMUP-1 (7-[2-[4-(2-chlorobenzene)piperazinyl]ethyl]-1,3-dimethylxanthine) blunts monocrotaline-induced pulmonary arterial hypertension by altering Ca2+sensitivity, K+-channel function, endothelial nitric oxide synthase activity, and RhoA/Rho kinase (ROCK) expression. This study further investigated whether KMUP-1 impedes uridine 5'-triphosphate (UTP)-inhibited delayed rectifying K+(KDR) current in rat pulmonary arteries involved the RhoA/ROCK signaling. Pulmonary artery smooth muscle cells (PASMCs) were enzymatically dissociated from rat pulmonary arteries. KMUP-1 (30μM) attenuated UTP (30μM)-mediated membrane depolarization and abolished UTP-enhanced cytosolic Ca2+concentration. Whole-cell patch-clamp electrophysiology was used to monitor KDRcurrents. A voltage-dependent KDRcurrent was isolated and shown to consist of a 4-aminopyridine (5mM)-sensitive component and an insensitive component. The 4-aminopyridine sensitive KDRcurrent was suppressed by UTP (30μM). The ROCK inhibitor Y27632 (30μM) abolished the ability of UTP to inhibit the KDRcurrent. Like Y27632, KMUP-1 (30μM) similarly abolished UTP-inhibited KDRcurrents. Superfused protein kinase A and protein kinase G inhibitors (KT5720, 300nM and KT5823, 300nM) did not affect UTP-inhibited KDRcurrents, but the currents were restored by adding KMUP-1 (30μM) to the superfusate. KMUP-1 reversal of KDRcurrent inhibition by UTP predominantly involves the ROCK inhibition. The results indicate that the RhoA/ROCK signaling pathway plays a key role in eliciting PASMCs depolarization caused by UTP, which would result in pulmonary artery constriction. KMUP-1 blocks UTP-mediated PASMCs depolarization, suggesting that it would prevent abnormal pulmonary vasoconstriction.
authors.affiliation: Department of Pediatrics, Division of Pediatric Pulmonology and Cardiology, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung, Taiwan.
authors.forename: Zen-Kong
authors.initials: ZK
authors.lastname: Dai
authors.affiliation: Department of Pharmacology, Graduate Institute of Medicine, College of Medicine, Lipid Science and Aging Research Center, Kaohsiung Medical University, Kaohsiung, Taiwan.
authors.forename: Chang-Ling
authors.initials: CL
authors.lastname: Kao
authors.affiliation: Department of Pharmacy, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan.
authors.forename: Su-Ling
authors.initials: SL
authors.lastname: Hsieh
authors.affiliation: Department of Pharmacology, Graduate Institute of Medicine, College of Medicine, Lipid Science and Aging Research Center, Kaohsiung Medical University, Kaohsiung, Taiwan.
authors.forename: Ing-Jun
authors.initials: IJ
authors.lastname: Chen
authors.affiliation: Department of Pharmacology, Graduate Institute of Medicine, College of Medicine, Lipid Science and Aging Research Center, Kaohsiung Medical University, Kaohsiung, Taiwan. Electronic address: binnan@kmu.edu.tw.
authors.forename: Bin-Nan
authors.initials: BN
authors.lastname: Wu
mesh_terms: D015761:4-Aminopyridine / Q000494:pharmacology; D000577:Amides / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D051668:Delayed Rectifier Potassium Channels / Q000378:metabolism*; D015536:Down-Regulation / Q000187:drug effects; D005260:Female; D015640:Ion Channel Gating / Q000187:drug effects; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D010880:Piperidines / Q000494:pharmacology*; D011651:Pulmonary Artery / Q000166:cytology*; D011725:Pyridines / Q000494:pharmacology; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects; D014544:Uridine Triphosphate / Q000494:pharmacology*; D014970:Xanthines / Q000494:pharmacology*; D054460:rho-Associated Kinases / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*
chemical_list: D000577:Amides; D051668:Delayed Rectifier Potassium Channels; D010880:Piperidines; D011725:Pyridines; D014970:Xanthines; C108830:Y 27632; C439304:KMUP 1; D009569:Nitric Oxide; D015761:4-Aminopyridine; D054460:rho-Associated Kinases; D020742:rhoA GTP-Binding Protein; D002118:Calcium; D014544:Uridine Triphosphate
keywords: K(DR) channels; KMUP-1; Patch-clamp electrophysiology; Pulmonary artery smooth muscle cells; RhoA/ROCK signaling