Platelet‐activating factor (PAF) acting via its receptor (PAFR) is implicated in the pathogenesis of persistent pulmonary hypertension of the newborn (PPHN). Effects of long‐term oxygen therapy on newborn lung are not well understood; therefore, we studied the effect of oxygen tension on ovine newborn pulmonary artery smooth muscle cells (NBPASMC). Our global hypothesis is that PPHN results from failure of newborn lamb pulmonary system to downregulate PAFR activity or to upregulate vasodilatory cyclic nucleotides (Cnucs) activity. NBPASMC from newborns 6–12 days old were studied in vitro at three different oxygen tensions (pO 2, [Torr]: hypoxia, <40; normoxia, 80–100; and hyperoxia, >100 Torr often clinically imposed upon newborns with PPHN). PAFR‐ and Cnucs mediated effects were determined. PAFR and PKA Cα mRNA expression as well as prostacyclin, thromboxane, cAMP production, and DNA synthesis was studied to assess PAFR‐mediated hypertrophy and/or hyperplasia. Hypoxia and hyperoxia increased specific PAFR binding. PAF treatment during hyperoxia increased PAFR gene, but decreased PKA‐Cα gene expression. Hypoxia and hyperoxia increased NBPASMC proliferation via PAFR signaling. Baseline prostacyclin level was ninefold greater than in fetal PASMC, whereas baseline thromboxane was sevenfold less suggesting greater postnatal cyclooxygenase activity in NBPASMC. PAF decreased, while forskolin and 8‐Br‐cAMP increased cAMP production. Decrease of PAFR effects by Cnucs indicates that normal newborn PA physiology favors vasodilator pathways to minimize PAF‐induced hypertrophy or hyperplasia. We speculate that failure of newborn lung to anchor downregulation of vasoconstrictors with upregulation of vasodilators leads to PPHN.

The basal ganglia including the caudate nucleus (CN) are critically involved in motor function with connections that include the sensorimotor sector of the thalamus. The CN, which has a high density of A2AR, has been implicated in the plasticity of the developing brain. We set out to identify intracellular signaling pathways in CN cells that are linked to A2AR activation that may be involved in neonatal brain plasticity. The hypothesis is that downstream effects of A2AR‐activation included modulation of cAMP/PKA signaling in CN cells. Culture of primary CN cells of neonatal lambs 4‐8d old were stimulated with different concentrations (uM, 10‐0.1) of CGS 21680 (CGS, A2AR agonist) compared to NECA. cAMP release and expression of A2AR, A1R, and PKA proteins were measured. Stimulation of cell proliferation by these agonists was also studied. CGS release of cAMP was dose‐dependent. A2AR antagonist SCH 58261(SCH) inhibited cAMP release. Also CGS increased while NECA decreased A2A receptor expression without affecting PKA expression. Both CGS and NECA stimulated caudate cell proliferation, PKA antagonist Rp‐cAMPS inhibited CGS stimulation of cell proliferation, A2AR, and PKA expression. These data show that cells from the caudate nucleus of neonatal lambs express functional A2AR and A1R that are linked to cAMP‐PKA signaling. These data may explain the greater plasticity of the neonatal brain attributed to the caudate nucleus. Supported by: Grant 20842: UCLA/LABiomed

Sickle cell chronic lung disease is one of the notable causes of death in patients with sickle cell disease (SCD). Prevention and treatment of acute chest syndrome (ACS) constitutes a major concern in clinical management of SCD. Some lung complications in SCD result from direct or indirect effect of pulmonary microvascular occlusion by sickle erythrocytes and their adhesion to the vascular endothelium. Vasoactive eicosanoids are released resulting in inflammatory response. Studies with HbSS mice have enhanced knowledge of SCD pathology, but the biochemical mechanisms of initiation and progression of ACS is not well understood. We hypothesized that lungs of SCD patients are under greater inflammatory stress due to decreased expression of anti‐inflammatory proteins and metabolites, but greater inflammatory proteins and metabolites. We studied baseline expression of 5‐Lox, cysLT1 as well as PKA, COX1 and COX2 and CREB and measured Leukotrienes and PGI2 release by lungs of HbSS mice and transgenic HbAA mice. HbSS mice lungs expressed 40‐60% more 5‐Lox and CysLT1, but 40‐70% less COX1/COX2 and CREB proteins; produced 68% greater LTs, but PGI2 was not detected. Expression of PKA was not different. The data suggest that SCD lungs are under greater inflammatory stress which may trigger ACS and sustain sickle cell chronic lung disease in SCD patients. Grant Funding Source: LA Biomed Seed grant 520522