title: Hyperoxia inhibits nitric oxide treatment effects in alveolar epithelial cells via effects on L-type amino acid transporter-1.
abstract: OBJECTIVE
  The aims of this study were to determine hyperoxia effects on S-nitrosothiol (SNO) accumulation and L-type amino acid transporter 1 (LAT1) expression/function in alveolar epithelium and to determine whether hyperoxia impairs exogenous nitric oxide (NO) treatment effects in alveolar epithelium through effects on LAT1 expression and/or function.
  
  
  RESULTS
  SNO accumulation in vitro and in vivo after NO treatment was dependent on the LAT1 system transport. Hyperoxia (60% or 90%) impaired NO effects on SNO accumulation and soluble guanylyl cyclase activation in proportion to the magnitude of hyperoxia and the duration of exposure, up to 12 h, in type I-like (R3/1) and type II-like (L2) rat and human (A549) alveolar epithelial cells. LAT function, determined by sodium-independent (3)H-leucine uptake, was impaired in a parallel manner. Hyperoxia impaired LAT1 expression in alveolar epithelial cells, determined by immunoblots and immunofluorescence, and in newborn rats exposed to 60% O2 for 4 days, determined by immunohistochemistry.
  
  
  METHODS
  Despite significant preclinical evidence, inhaled NO has shown disappointing limitations in clinical applications. Our studies suggest an important explanation: oxidative stress, a common feature of diseases in which therapeutic NO would be considered, impairs LAT1 expression and function, blocking a major route for inhaled NO (iNO) action, that is, the uptake of S-nitrosocysteine via LAT1.
  
  
  CONCLUSIONS
  SNO uptake after NO treatment is dependent on LAT1. Hyperoxia impairs SNO uptake and NO effects during NO exposure and impairs LAT system function and LAT1 expression. Effects on SNO formation and transport must be considered for rational optimization of NO-based therapeutics.
authors.affiliation: 1 Department of Pediatrics, Duke University Medical Center , Durham, North Carolina.
authors.forename: Mulugu V
authors.initials: MV
authors.lastname: Brahmajothi
authors.forename: Brian T
authors.initials: BT
authors.lastname: Tinch
authors.forename: Michael F
authors.initials: MF
authors.lastname: Wempe
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Endou
authors.forename: Richard L
authors.initials: RL
authors.lastname: Auten
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000502:physiology; D045744:Cell Line, Tumor; D003545:Cysteine / Q000031:analogs & derivatives / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism* / Q000473:pathology; D006162:Guanylate Cyclase / Q000378:metabolism; D006801:Humans; D018496:Hyperoxia / Q000378:metabolism / Q000473:pathology*; D027283:Large Neutral Amino Acid-Transporter 1 / Q000378:metabolism*; D007930:Leucine / Q000378:metabolism; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism*; D018384:Oxidative Stress / Q000502:physiology; D011650:Pulmonary Alveoli / Q000378:metabolism* / Q000473:pathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D026403:S-Nitrosothiols / Q000378:metabolism; D000071756:Soluble Guanylyl Cyclase
chemical_list: D027283:Large Neutral Amino Acid-Transporter 1; D018160:Receptors, Cytoplasmic and Nuclear; D026403:S-Nitrosothiols; D009569:Nitric Oxide; C021315:S-nitrosocysteine; D006162:Guanylate Cyclase; D000071756:Soluble Guanylyl Cyclase; D007930:Leucine; D003545:Cysteine
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