title: Alcohol decreases RhoA activity through a nitric oxide (NO)/cyclic GMP(cGMP)/protein kinase G (PKG)-dependent pathway in the airway epithelium.
abstract: BACKGROUND
  Alcohol has been shown to have a number of harmful effects on the lung, including increasing the risk of pneumonia and bronchitis. How alcohol increases the risk of these diseases is poorly defined. RhoA is a small guanosine triphosphate (GTP)ase that plays an integral role in many basic functions of airway epithelial cells. It is not known how alcohol affects RhoA activity in the airway epithelium. We hypothesized that brief alcohol exposure modulates RhoA activity in the airway epithelium through a nitric oxide (NO)/cyclic GMP (cGMP)/protein kinase G (PKG)-dependent pathway.
  
  
  METHODS
  Primary airway epithelial cells were cultured and exposed to ethanol at various concentrations and times. The cell layers were harvested and RhoA activity was measured.
  
  
  RESULTS
  Alcohol induced a time- and concentration-dependent decrease in RhoA activity in airway epithelial cells. We were able to block this decrease in activity using Nω-nitro-l-arginine methyl ester (L-NAME) hydrochloride, a nitric oxide synthase (NOS) inhibitor. Likewise, we were able to demonstrate the same decrease in RhoA activation using 0.1 μM sodium nitroprusside, an NO donor. To determine the role of cGMP/PKG, we pretreated the cells with a cGMP antagonist analog, Rp-8Br-cGMPS. This blocked the decrease in RhoA activity caused by alcohol, suggesting that alcohol exerts its effect on RhoA activity through cGMP/PKG.
  
  
  CONCLUSIONS
  Alcohol decreases airway epithelial RhoA activity through an NO/cGMP/PKG-dependent pathway. RhoA activity controls many aspects of basic cellular function, including cell morphology, tight junction formation, and cell cycle progression and gene regulation. Dysregulation of RhoA activity can potentially have several consequences, including dysregulation of inflammation. This may partially explain how alcohol increases the risk of pneumonia and bronchitis.
authors.affiliation: Pulmonary, Critical Care, Sleep & Allergy Division, University of Nebraska Medical Center, Omaha, NE 68198, USA. kbailey@unmc.edu
authors.forename: Kristina L
authors.initials: KL
authors.lastname: Bailey
authors.forename: James E
authors.initials: JE
authors.lastname: Robinson
authors.forename: Joseph H
authors.initials: JH
authors.lastname: Sisson
authors.forename: Todd A
authors.initials: TA
authors.lastname: Wyatt
mesh_terms: D002478:Cells, Cultured; D006152:Cyclic GMP / Q000502:physiology*; D017869:Cyclic GMP-Dependent Protein Kinases / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000187:drug effects / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D000431:Ethanol / Q000494:pharmacology*; D006801:Humans; D009569:Nitric Oxide / Q000502:physiology*; D020545:Respiratory Mucosa / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D020742:rhoA GTP-Binding Protein / Q000037:antagonists & inhibitors / Q000502:physiology*
chemical_list: D004791:Enzyme Inhibitors; D009569:Nitric Oxide; D000431:Ethanol; D017869:Cyclic GMP-Dependent Protein Kinases; D020742:rhoA GTP-Binding Protein; D006152:Cyclic GMP