title: The effectiveness of oral tin mesoporphyrin prophylaxis in reducing bilirubin production after an oral heme load in a transgenic mouse model.
abstract: BACKGROUND
  Neonatal jaundice is commonly encountered and rarely associated with morbidity and mortality. Nonetheless, infants with glucose-6-phosphate dehydrogenase deficiency often have hemolysis (a heme load) caused by an environmental oxidant trigger, thus increasing their risk for serious morbidity. The use of tin mesoporphyrin (SnMP) has been proposed for interdicting the development of severe hyperbilirubinemia in a variety of conditions.
  
  
  OBJECTIVE
  We studied the in vivo effects of prophylactic oral SnMP on heme oxygenase (HO) activity and bilirubin production, as indexed by the excretion rate of carbon monoxide (VeCO), following a subsequent oral heme load.
  
  
  METHODS
  Adult mice were exposed serially to heme and assessed for in vivo bilirubin production rates, HO-1 transcription and protein, and HO activity. The effect of prophylaxis with a single oral dose of SnMP prior to an oral heme load was assessed by measuring VeCOand tissue HO activities.
  
  
  RESULTS
  After serial heme exposures, VeCO, HO-1 transcription and protein, and liver and spleen HO activities increased incrementally. After pretreatment with oral SnMP, bilirubin production decreased in response to an oral heme load. Also, heme-mediated increases in liver, spleen, and intestine HO activities were significantly dampened.
  
  
  CONCLUSIONS
  A single oral dose of SnMP results in durable inhibition of bilirubin production and HO activity for at least 24 h in a mouse model of oral heme loading. Further studies are needed to fully elucidate the duration of this protection against hyperbilirubinemia due to a delayed heme load and any long-term consequences of prophylaxis with SnMP on HO-1 transcription and HO-1 protein.
authors.affiliation: Department of Pediatrics, Stanford University School of Medicine, Stanford, CA 94306, USA.
authors.forename: Glenn H
authors.initials: GH
authors.lastname: DeSandre
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Wong
authors.forename: Ichiro
authors.initials: I
authors.lastname: Morioka
authors.forename: Christopher H
authors.initials: CH
authors.lastname: Contag
authors.forename: David K
authors.initials: DK
authors.lastname: Stevenson
mesh_terms: D000818:Animals; D001663:Bilirubin / Q000096:biosynthesis*; D002248:Carbon Monoxide / Q000032:analysis; D004195:Disease Models, Animal; D006418:Heme / Q000008:administration & dosage*; D051547:Heme Oxygenase-1 / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D006932:Hyperbilirubinemia / Q000517:prevention & control*; D008665:Metalloporphyrins / Q000627:therapeutic use*; D051379:Mice; D008822:Mice, Transgenic; D014158:Transcription, Genetic
chemical_list: D008665:Metalloporphyrins; C055421:tin mesoporphyrin; D006418:Heme; D002248:Carbon Monoxide; D051547:Heme Oxygenase-1; D001663:Bilirubin