title: Corpus cavernosal smooth muscle relaxation effect of a novel AMPK activator, beta-lapachone.
abstract: BACKGROUND
  Adenosine monophosphate-activated protein kinase (AMPK) activation is suggested to relax smooth muscle by endothelial nitric oxide synthase (eNOS) phosphorylation.
  
  
  OBJECTIVE
  To assess the mechanism and effect of a novel AMPK activator, beta-lapachone, upon cavernosal smooth muscle relaxation and the therapeutic potential for erectile dysfunction.
  
  
  METHODS
  Human umbilical vein endothelial cells (HUVECs) were treated with beta-lapachone. The lysates were blotted with specific antibodies for phosphorylated AMPK (p-AMPK) or phosphorylated eNOS (p-eNOS). The membranes were re-blotted for total AMP total eNOS, or beta-actin. The eNOS activity was measured by the conversion of L-14C-arginine to L-14C-citrulline in HUVECs lysates. In a separated experiment, cavernosal strips from New Zealand white rabbits were harvested for organ bath study and the relaxation effect of beta-lapachone on phenylephrine-induced contracted strips was evaluated and compared with sodium nitroprusside, zaprinast, metformin, and aminoimidazole carboxamide ribonucleotide (AICAR). Methylene blue and L-NAME were used to assess the inhibition of cyclic guanosine monophosphate/nitric oxide pathway. Zinc-protoporphyrin-IX (ZnPP) was also used to investigate the contribution of mevalonate pathway.
  
  
  METHODS
  The expression of p-AMPK, p-eNOS, AMPK and eNOS induced by beta-lapachone in HUVECs study and the percent relaxation of cavernosal tissue in organ bath study.
  
  
  RESULTS
  Beta-lapachone clearly induced AMPK phosphorylation and, as a consequence, eNOS phosphorylation in HUVECs. Beta-lapachone-induced upregulation of eNOS activity was also observed in HUVECs and steadily increased up to 1 hour. In organ bath study, beta-lapachone significantly relaxed the phenylephrine pretreated strips in a dose-dependent manner. This relaxation effect was not totally blocked by methylene blue or L-NAME. After removing endothelium, the relaxation was totally blocked by ZnPP.
  
  
  CONCLUSIONS
  A novel AMPK activator, beta-lapachone has a strong relaxation effect on precontracted cavernosal smooth muscle strips in the rabbit. And phosphorylation of AMPK and eNOS strongly related to the action of beta-lapachone. Mevalonate pathway also might be considered as a suggestive mechanism.
authors.affiliation: Department of Urology, Korea University Medical Center and Korea University Institute of Regenerative Medicine, Seoul, Korea.
authors.forename: Jae Hyun
authors.initials: JH
authors.lastname: Bae
authors.forename: Jin Wook
authors.initials: JW
authors.lastname: Kim
authors.forename: Gi Ryang
authors.initials: GR
authors.lastname: Kweon
authors.forename: Myoung Gyu
authors.initials: MG
authors.lastname: Park
authors.forename: Kyeong-Hoon
authors.initials: KH
authors.lastname: Jeong
authors.forename: Je Jong
authors.initials: JJ
authors.lastname: Kim
authors.forename: Du Geon
authors.initials: du G
authors.lastname: Moon
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000378:metabolism*; D000818:Animals; D061307:Human Umbilical Vein Endothelial Cells / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects; D009285:Naphthoquinones / Q000494:pharmacology*; D009465:Neuromuscular Agents / Q000494:pharmacology*; D052250:Nitric Oxide Synthase Type III / Q000096:biosynthesis / Q000378:metabolism*; D010413:Penis / Q000187:drug effects* / Q000378:metabolism; D010766:Phosphorylation; D011817:Rabbits
chemical_list: D009285:Naphthoquinones; D009465:Neuromuscular Agents; C014638:beta-lapachone; D052250:Nitric Oxide Synthase Type III; D055372:AMP-Activated Protein Kinases