Adrenomedullin reduces intestinal epithelial permeability in vivo and in vitro

Am J Physiol Gastrointest Liver Physiol. 2009 Jul;297(1):G43-51. doi: 10.1152/ajpgi.90532.2008. Epub 2009 May 7.

Abstract

Leakage of the gut mucosal barrier in the critically ill patient may allow translocation of bacteria and their virulence factors, thereby perpetuating sepsis and inflammation. Present evidence suggests that adrenomedullin (AM) improves endothelial barrier function and stabilizes circulatory function in systemic inflammation. We tested the hypothesis that exogenously applied AM stabilizes gut epithelial barrier function. Infusion of Staphylococcus aureus alpha-toxin induced septic shock in rats. AM infusion in a therapeutic setting reduced translocation of labeled dextran from the gut into the systemic circulation in this model. AM also reduced alpha-toxin and hydrogen peroxide (H2O2)-related barrier disruption in Caco-2 cells in vitro and reduced H2O2-related rat colon barrier malfunction in Ussing chamber experiments. AM was shown to protect endothelial barrier function via cAMP elevation, but AM failed to induce cAMP accumulation in Caco-2 cells. cAMP is degraded via phosphodiesterases (PDE), and Caco-2 cells showed high activity of cAMP-degrading PDE3 and 4. However, AM failed to induce cAMP accumulation in Caco-2 cells even in the presence of sufficient PDE3/4 inhibition, whereas adenylyl cyclase activator forskolin induced strong cAMP elevation. Furthermore, PDE3/4 inhibition neither amplified AM-induced epithelial barrier stabilization nor affected AM cAMP-related rat colon short-circuit current, furthermore indicating that AM may act independently of cAMP in Caco-2 cells. Finally, experiments using chemical inhibitors indicated that PKC, phosphatidylinositide 3-kinase, p38, and ERK did not contribute to AM-related stabilization of barrier function in Caco-2 cells. In summary, during severe inflammation, elevated AM levels may substantially contribute to the stabilization of gut barrier function.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adrenomedullin / administration & dosage
  • Adrenomedullin / metabolism*
  • Animals
  • Bacterial Toxins
  • Bacterial Translocation* / drug effects
  • Caco-2 Cells
  • Colon / drug effects
  • Colon / metabolism*
  • Cyclic AMP / metabolism
  • Cyclic Nucleotide Phosphodiesterases, Type 3 / metabolism
  • Cyclic Nucleotide Phosphodiesterases, Type 4 / metabolism
  • Dextrans / metabolism
  • Disease Models, Animal
  • Enzyme Activators / pharmacology
  • Extracellular Signal-Regulated MAP Kinases / metabolism
  • Fluorescein-5-isothiocyanate / analogs & derivatives
  • Fluorescein-5-isothiocyanate / metabolism
  • Fluorescent Dyes / metabolism
  • Hemolysin Proteins
  • Humans
  • Hydrogen Peroxide / toxicity
  • Ileum / drug effects
  • Ileum / metabolism*
  • Infusions, Intravenous
  • Intestinal Mucosa / drug effects
  • Intestinal Mucosa / metabolism*
  • Male
  • Permeability
  • Phosphatidylinositol 3-Kinases / metabolism
  • Phosphodiesterase Inhibitors / pharmacology
  • Protein Kinase C / metabolism
  • Protein Kinase Inhibitors / pharmacology
  • Rats
  • Rats, Sprague-Dawley
  • Shock, Septic / chemically induced
  • Shock, Septic / metabolism*
  • Signal Transduction
  • Time Factors
  • p38 Mitogen-Activated Protein Kinases / metabolism

Substances

  • Bacterial Toxins
  • Dextrans
  • Enzyme Activators
  • Fluorescent Dyes
  • Hemolysin Proteins
  • Phosphodiesterase Inhibitors
  • Protein Kinase Inhibitors
  • fluorescein isothiocyanate dextran
  • staphylococcal alpha-toxin
  • Adrenomedullin
  • Hydrogen Peroxide
  • Cyclic AMP
  • Phosphatidylinositol 3-Kinases
  • Protein Kinase C
  • Extracellular Signal-Regulated MAP Kinases
  • p38 Mitogen-Activated Protein Kinases
  • Cyclic Nucleotide Phosphodiesterases, Type 3
  • Cyclic Nucleotide Phosphodiesterases, Type 4
  • Fluorescein-5-isothiocyanate