EXPRESSION OF PLATELET-ACTIVATING-FACTOR RECEPTOR MESSENGER-RNA IN HUMAN AND GUINEA-PIG LUNG

Platelet-activating factor (PAF) has been implicated in the pathogenes is of several inflammatory pulmonary diseases, and specific binding si tes have been demonstrated in human and guinea pig lung membranes by r adioligand binding experiments. Both human and guinea pig PAF receptor s (PAFR) have recently been cloned. We have used molecular probes to s tudy the gene expression of PAFR in human and animal lung and in situ hybridization to determine the distribution of PAFR mRNA in peripheral lung. Northern blot analysis of total lung RNA from human lung parenc hyma, using a 1.1-kb SmaI-EcoRI fragment of human PAFR cDNA or a 0.9-k b SmaI-SmaI fragment of guinea pig PAFR cDNA, demonstrated the express ion of PAFR mRNA in human lung, with a single transcript of 4 kb. Ther e was a significant increase in PAFR mRNA in the lungs of asthmatic pa tients and a significant decrease in PAFR mRNA in the lungs of cigaret te smokers compared with normal patients. Similarly, the expression of PAFR mRNA on guinea pig and rat lung was detected as a single transcr ipt of 3 kb, using both guinea pig and human PAFR cDNA probes. A full- length 1.8-kb human leukocyte PAFR cDNA probe was used as the DNA temp late for producing ''S-labeled antisense and sense cRNA probes for use in in situ hybridization studies of human peripheral lung. These stud ies revealed high levels of PAFR mRNA hybridization in blood vessels, moderate levels of hybridization in alveolar walls and peripheral airw ay smooth muscle, but no specific signal in airway epithelium. To stud y the possible modulation of PAFR mRNA expression, we performed Northe rn blot analysis on lung from sensitized guinea pigs chronically expos ed to aerosolized allergen and from rats chronically treated with dexa methasone. However, these manipulations did not cause any significant change in PAFR mRNA levels.