Responses of pulmonary platelet-derived growth factor peptides and receptors to hyperoxia and nitric oxide in piglet lungs

The peptides platelet-derived growth factor-A (PDGF-A) and especially -B have important roles in lung development. The effect of hyperoxic exposure with and without inhaled nitric oxide (iNO) on lung expression of PDGF and its receptors is unknown. We hypothesized that hyperoxia exposure would suppress mRNA expression and protein production of these ligands and their receptors. The addition of iNO to hyperoxia may further aggravate the effects of hyperoxia. Thirteen-day-old piglets were randomized to breathe 1) room air (RA); 2) 0.96 fraction of inspired oxygen (O₂), or 3) 0.96 fraction of inspired oxygen plus 50 ppm of NO (O₂ + NO), for 5 d. Lungs were preserved for mRNA, Western immunoblot, and immunohistochemical analyses for PDGF-A and -B and their receptors PDGFR-α and -β. PDGF-B mRNA expression was greater than that of PDGF-A or PDGFR-α and -β in RA piglet lungs (p < 0.05). Hyperoxia with or without iNO reduced lung PDGF-B mRNA and protein expression relative to the RA group lungs (p < 0.01). PDGF-B immunostain intensity was significantly increased in the alveolar macrophages, which were present in greater numbers in the hyperoxia-exposed piglet lungs, with or without NO (p < 0.01). PDGFR-β immunostaining was significantly increased in airway epithelial cells in O₂- and O₂ + NO-exposed piglets. PDGF-A and PDGFR-α immunostain intensity and distribution pattern were unchanged relative to the RA group. Sublethal hyperoxia decreases PDGF-B mRNA and protein expression but not PDGF-A or their receptors in piglet lungs. iNO neither aggravates nor ameliorates this effect.