title: Inhibitory effect of rhynchophylline on contraction of cerebral arterioles to endothelin 1: role of rho kinase.
abstract: BACKGROUND
  Rhynchophylline (Rhy) is a major ingredient of Uncaria rhynchophylla (UR) used to reduce blood pressure and ameliorate brain ailments. This study was to examine the role of Rho kinase (ROCK) in the inhibition of Rhy on contraction of cerebral arterioles caused by endothelin 1 (ET-1).
  
  
  METHODS
  Cerebral arterioles of male Wistar rats were constricted with ET-1 for 10 min followed by perfusion of Rhy for 20 min. Changes in the diameters of the arterioles were recorded. The effects of Rhy on contraction of middle cerebral arteries (MCAs) were determined by a Multi-Myograph. Western blotting and immunofluorescent staining were used to examine the effects of Rhy on RhoA translocation and myosin phosphatase target subunit 1 (MYPT1) phosphorylation.
  
  
  RESULTS
  In vivo, Rhy (30-300 µM) relaxed cerebral arterioles constricted with ET-1 dose-dependently. In vitro, Rhy at lower concentrations (1-100 µM) caused relaxation of rat MCAs constricted with KCl and Bay-K8644 (an agonist of L-type voltage-dependent calcium channels (L-VDCCs)). Rhy at higher concentrations (>100 µM) caused relaxation of rat MCAs constricted with ET-1, which was inhibited by Y27632, a ROCK׳s inhibitor. Western blotting of rat aortas showed that Rhy inhibited RhoA translocation and MYPT1 phosphorylation. Immunofluorescent staining of MCAs confirmed that phosphorylation of MYPT1 caused by ET-1 was inhibited by Rhy.
  
  
  CONCLUSIONS
  These results demonstrate that Rhy is a potent inhibitor of contraction of cerebral arteries caused by ET-1 in vivo and in vitro. The effect of Rhy was in part mediated by inhibiting RhoA-ROCK signaling.
authors.affiliation: Tasly Microcirculation Research Center, Peking University Health Science Center, Beijing 100191, China; Department of Integration of Chinese and Western Medicine, School of Basic Medical Sciences, Peking University, 38 Xue Yuan Road, Beijing 100191, China.
authors.forename: Hui-Feng
authors.initials: HF
authors.lastname: Hao
authors.affiliation: Department of Physiology and Pathophysiology, Peking University Health Science Center, 38 Xue Yuan Road, Beijing 100191, China.
authors.forename: Li-Mei
authors.initials: LM
authors.lastname: Liu
authors.affiliation: Tasly Microcirculation Research Center, Peking University Health Science Center, Beijing 100191, China.
authors.forename: Yu-Ying
authors.initials: YY
authors.lastname: Liu
authors.affiliation: Department of Physiology and Pathophysiology, Peking University Health Science Center, 38 Xue Yuan Road, Beijing 100191, China.
authors.forename: Juan
authors.initials: J
authors.lastname: Liu
authors.affiliation: Tasly Microcirculation Research Center, Peking University Health Science Center, Beijing 100191, China.
authors.forename: Li
authors.initials: L
authors.lastname: Yan
authors.affiliation: Tasly Microcirculation Research Center, Peking University Health Science Center, Beijing 100191, China.
authors.forename: Chun-Shui
authors.initials: CS
authors.lastname: Pan
authors.affiliation: Tasly Microcirculation Research Center, Peking University Health Science Center, Beijing 100191, China.
authors.forename: Ming-Xia
authors.initials: MX
authors.lastname: Wang
authors.affiliation: Tasly Microcirculation Research Center, Peking University Health Science Center, Beijing 100191, China; Department of Integration of Chinese and Western Medicine, School of Basic Medical Sciences, Peking University, 38 Xue Yuan Road, Beijing 100191, China.
authors.forename: Chuan-She
authors.initials: CS
authors.lastname: Wang
authors.affiliation: Tasly Microcirculation Research Center, Peking University Health Science Center, Beijing 100191, China.
authors.forename: Jing-Yu
authors.initials: JY
authors.lastname: Fan
authors.affiliation: Department of Physiology and Pathophysiology, Peking University Health Science Center, 38 Xue Yuan Road, Beijing 100191, China. Electronic address: ygao@bjmu.edu.cn.
authors.forename: Yuan-Sheng
authors.initials: YS
authors.lastname: Gao
authors.affiliation: Tasly Microcirculation Research Center, Peking University Health Science Center, Beijing 100191, China; Department of Integration of Chinese and Western Medicine, School of Basic Medical Sciences, Peking University, 38 Xue Yuan Road, Beijing 100191, China. Electronic address: hanjingyan@bjmu.edu.cn.
authors.forename: Jing-Yan
authors.initials: JY
authors.lastname: Han
mesh_terms: D000818:Animals; D001160:Arterioles / Q000187:drug effects* / Q000378:metabolism; D054022:Cerebrum / Q000098:blood supply / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D019332:Endothelin-1 / Q000378:metabolism*; D026121:Indole Alkaloids / Q000008:administration & dosage / Q000302:isolation & purification / Q000494:pharmacology*; D008297:Male; D000078183:Oxindoles; D010766:Phosphorylation / Q000187:drug effects; D054645:Protein Phosphatase 1 / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D032070:Uncaria / Q000737:chemistry*; D014661:Vasoconstriction / Q000187:drug effects; D014664:Vasodilation / Q000187:drug effects; D054460:rho-Associated Kinases / Q000378:metabolism
chemical_list: D019332:Endothelin-1; D026121:Indole Alkaloids; D000078183:Oxindoles; C052714:rhyncophylline; D054460:rho-Associated Kinases; C499850:Ppp1r12a protein, rat; D054645:Protein Phosphatase 1
keywords: Endothelin 1; L-VDCC; RhoA–ROCK; Vasodilation