title: Epithelial inducible nitric oxide synthase causes bacterial translocation by impairment of enterocytic tight junctions via intracellular signals of Rho-associated kinase and protein kinase C zeta.
abstract: OBJECTIVE
  Gut barrier dysfunction and bacterial translocation occur in various disorders, including intestinal obstruction. Overexpression of inducible nitric oxide synthase is implicated in the pathogenesis of bacterial translocation, of which the molecular mechanism remains unclear. Epithelial permeability is regulated by tight junction reorganization and myosin light chain phosphorylation. Our aim was to investigate the roles of Rho-associated kinase and protein kinase C ζ in epithelial nitric oxide synthase-mediated barrier damage.
  
  
  METHODS
  Animal study and cell cultures.
  
  
  METHODS
  Research laboratory.
  
  
  METHODS
  BALB/c mice.
  
  
  METHODS
  : Mouse distal small intestine was obstructed in vivo by a 10-cm loop ligation in which vehicle, L-Nil (a nitric oxide synthase inhibitor), or Y27632 (a Rho-associated kinase inhibitor) was luminally administered. After obstruction for 24 hrs, intestinal tissues were mounted on Ussing chambers for macromolecular flux. Liver and spleen tissues were assessed for bacterial counts. Caco-2 cells were exposed to 1 mM S-nitroso-N-acetylpenicillamine (a nitric oxide donor) for 24 hrs, and transepithelial resistance and permeability were evaluated.
  
  
  RESULTS
  Mice with intestinal obstruction displayed epithelial barrier dysfunctions, such as permeability rise and bacterial translocation, associated with tight junction disruption and myosin light chain phosphorylation. Increased inducible nitric oxide synthase and phosphorylated protein kinase C ζ were observed in villus epithelium. Enteric instillation of L-Nil and Y27632 attenuated the functional and structural barrier damage caused by intestinal obstruction. L-Nil decreased intestinal obstruction-induced myosin light chain, myosin phosphatase target subunit 1, and protein kinase C ζ phosphorylation, suggesting that inducible nitric oxide synthase is upstream of Rho-associated kinase and protein kinase C ζ signaling. The intestinal phosphorylated myosin light chain level did not increase in inducible nitric oxide synthase(-/-) mice following intestinal obstruction. In vitro studies showed that S-nitroso-N-acetylpenicillamine-induced transepithelial resistance drop and permeability rise was independent of cell apoptosis. Y27632 inhibited S-nitroso-N-acetylpenicillamine-induced myosin light chain phosphorylation and permeability rise. S-nitroso-N-acetylpenicillamine also triggered phosphorylation and membrane translocation of protein kinase C ζ. Inhibitory protein kinase C ζ pseudosubstrate blocked S-nitroso-N-acetylpenicillamine-induced tight junction reorganization, but not myosin light chain phosphorylation.
  
  
  CONCLUSIONS
  Epithelial inducible nitric oxide synthase activates two distinct signals, protein kinase C ζ and Rho-associated kinase, to disrupt tight junctions leading to bacterial influx.
authors.affiliation: Graduate Institutes of Physiology, National Taiwan University College of Medicine, Taipei, Taiwan. lchyu@ntu.edu.tw
authors.forename: Li-Ling
authors.initials: LL
authors.lastname: Wu
authors.forename: Hsin-Da
authors.initials: HD
authors.lastname: Chiu
authors.forename: Wei-Hao
authors.initials: WH
authors.lastname: Peng
authors.forename: Bor-Ru
authors.initials: BR
authors.lastname: Lin
authors.forename: Kuo-Shyan
authors.initials: KS
authors.lastname: Lu
authors.forename: Yen-Zhen
authors.initials: YZ
authors.lastname: Lu
authors.forename: Linda Chia-Hui
authors.initials: LC
authors.lastname: Yu
mesh_terms: D000577:Amides / Q000494:pharmacology; D000818:Animals; D018988:Bacterial Translocation / Q000502:physiology*; D018938:Caco-2 Cells / Q000502:physiology; D018929:Cell Culture Techniques; D002463:Cell Membrane Permeability / Q000502:physiology; D020895:Enterocytes / Q000201:enzymology / Q000502:physiology*; D006801:Humans; D007415:Intestinal Obstruction / Q000201:enzymology / Q000382:microbiology / Q000503:physiopathology; D008099:Liver / Q000382:microbiology; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D052247:Nitric Oxide Synthase Type II / Q000502:physiology*; D011493:Protein Kinase C / Q000502:physiology*; D011725:Pyridines / Q000494:pharmacology; D015398:Signal Transduction / Q000502:physiology; D013154:Spleen / Q000382:microbiology; D019108:Tight Junctions / Q000201:enzymology / Q000382:microbiology / Q000502:physiology*; D054460:rho-Associated Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*; D000099221:Protein Kinase C zeta
chemical_list: D000577:Amides; D052247:Nitric Oxide Synthase Type II; D011493:Protein Kinase C; D011725:Pyridines; D054460:rho-Associated Kinases; D000099221:Protein Kinase C zeta; C108830:Y 27632; C496317:Nos2 protein, mouse