ALTERNATIVE SPLICING OF PECAM-1 mRNA DURING HYPEROXIC LUNG INJURY. † 2055

Lung injury is a frequent consequence of O₂ therapy administered to newborn and adults with respiratory distress and results in important mortality and morbidity. Acute exposure to hyperoxia results in a well-described pathophysiologic response, beginning with subtle, subcellular changes and ending with severe pulmonary inflammation and edema. The appearance of neutrophils is associated with marked accentuation of lung injury. Platelet/endothelial cell adhesion molecule 1 (PECAM-1), a member of the immunoglobulin superfamily that is expressed at the junctions between endothelial cells, is essential to the transendothelial migration of leukocytes. Alternative splicing of the cytoplasmic domain of PECAM-1 mRNA has been documented in vivo during embryonic heart development and has been shown to produce modification in ligand properties in vitro. We have previously shown an increase of PECAM-1 expression in the endothelium of lung exposed to hyperoxia. In this study, PECAM isoform expression was studied in lung of adult male mice exposed to hyperoxia up to 96h. Whole-lung RNA from controls and hyperoxia-exposed animals were reversed transcribed (RT) and amplified by polymerase chain reaction (PCR) using primer pairs that flank the cytoplasmic domain. The down-stream primer was labeled with P³² and the PCR products were separated on polycrylamide gels before autoradiography. At least 7 isoforms of PECAM-1 were detected in lung of control mice with a predominance of a middle size isoform; the isoform with the full length cytoplasmic domain accounted for less than 20% of the total PECAM-1 mRNA. No additional isoform was seen following hyperoxia, but a variations in the abundance of each isoforms was observed. Characterization of the isoforms are underway. The biological significance of the alternative splicing of PECAM-1 mRNA is still unknown, however the demonstration of isoform specific regulation suggest that its role is not restricted to organ development(Quebec Pulmonary Association, Queen Elizabeth II Research fund, Téléthon de la Recherche sur les Maladies Infantiles).