In vivo inosine protects alveolar epithelial type 2 cells against hyperoxia-induced DNA damage through MAP kinase signaling

Am J Physiol Lung Cell Mol Physiol. 2005 Mar;288(3):L569-75. doi: 10.1152/ajplung.00278.2004. Epub 2004 Dec 3.

Abstract

Inosine, a naturally occurring purine with anti-inflammatory properties, was assessed as a possible modulator of hyperoxic damage to the pulmonary alveolar epithelium. Rats were treated with inosine, 200 mg/kg ip, twice daily during 48-h exposure to >90% oxygen. The alveolar epithelial type 2 cells (AEC2) were then isolated and cultured. AEC2 isolated from inosine-treated hyperoxic rats had less DNA damage and had increased antioxidant status compared with AEC2 from hyperoxic rats. Inosine treatment during hyperoxia also reduced the proportion of AEC2 in S and G2/M phases of the cell cycle and increased levels of the DNA repair enzyme 8-oxoguanine DNA glycosylase. Bronchoalveolar lavage (BAL) recovered from hyperoxic, inosine-treated rats contained threefold higher levels of active transforming growth factor-beta than BAL from rats exposed to hyperoxia alone, and Smad2 was activated in AEC2 isolated from these animals. ERK1/2 was activated both in freshly isolated and 24-h-cultured AEC2 by in vivo inosine treatment, whereas blockade of the MAPK pathway in vitro reduced the protective effect of in the vivo inosine treatment. Together, the data suggest that inosine treatment during hyperoxic exposure results in protective signaling mediated through pathways downstream of MEK. Thus inosine may deserve further evaluation for its potential to reduce hyperoxic damage to the pulmonary alveolar epithelium.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Bronchoalveolar Lavage Fluid / chemistry
  • Cell Cycle
  • Cells, Cultured
  • Cytoprotection*
  • DNA Damage* / drug effects
  • DNA Glycosylases / metabolism
  • DNA-Binding Proteins / metabolism
  • Enzyme Activation / drug effects
  • Epithelial Cells / drug effects
  • Epithelial Cells / metabolism
  • Epithelial Cells / pathology
  • Extracellular Signal-Regulated MAP Kinases / metabolism
  • Flavonoids / pharmacology
  • Glutathione / blood
  • Hyperoxia / genetics
  • Hyperoxia / metabolism
  • Hyperoxia / pathology
  • Hyperoxia / physiopathology*
  • Inosine / pharmacology*
  • MAP Kinase Signaling System*
  • Male
  • Mitogen-Activated Protein Kinase Kinases / antagonists & inhibitors
  • Pulmonary Alveoli / drug effects
  • Pulmonary Alveoli / metabolism
  • Pulmonary Alveoli / pathology
  • Pulmonary Alveoli / physiopathology*
  • Rats
  • Rats, Sprague-Dawley
  • Smad2 Protein
  • Trans-Activators / metabolism
  • Transforming Growth Factor beta / metabolism
  • Uric Acid / pharmacology

Substances

  • DNA-Binding Proteins
  • Flavonoids
  • Smad2 Protein
  • Smad2 protein, rat
  • Trans-Activators
  • Transforming Growth Factor beta
  • Uric Acid
  • Inosine
  • Extracellular Signal-Regulated MAP Kinases
  • Mitogen-Activated Protein Kinase Kinases
  • DNA Glycosylases
  • OGG1 protein, rat
  • Glutathione
  • 2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one