Inhibition of meconium induced activation of granulocytes from neonates and adults by pentoxyphylline

Abstract

Neutrophil activation plays a crucial role in the pathogenesis of the meconium aspiration syndrome. Therefore antiinflammatory strategies may offer therapeutic options. The methylxanthinderivative pentoxyphylline (PTX) is known to inhibit the tumor necrosis factor alpha-synthesis and neutrophil degranulation and thus may have beneficial effects on meconium-induced pulmonary inflammation. Effects of PTX on PMN-degranulation in neonatal whole blood have not yet been studied. Heparin-anticoagulated (3 IE/ml) whole blood of healthy neonates (n = 6) and adult volunteers (n = 6) was incubated for 45 min. Spontaneous PMN-degranulation was compared with meconium-induced (3 mg/ml) and PTX-inhibited (0,025 - 0,4 mg/ml) degranulation by means of elastase (EL) and lactoferrin (LF) release from azurophilic and specific granules. EL- and LF plasma concentration was measured by immunoluminometric methods. Spontaneous degranulation of neonatal PMN was found to be significantly increased after 15 minutes compared with cells from adults (EL and LF concentration: 674 and 660 ng/10 6 PMN vs. 284 and 261 ng/10 6 PMN). At 45 minutes adult PMN showed an acceleration of degranulation in contrast to neonatal cells (EL and LF: 1827 and 1232 ng/10 6 PMN vs. 1400 and 860 ng/10 6 PMN). In presence of PTX (0,4 mg/ml) spontaneous release of EL and LF from neonatal PMN was inhibited by nearly 70 % at 45 min. while degranulation from adult PMN was found to be completely inhibited at 15 min. and reduced by 82 % and 78 % at 45 min. In presence of meconium (3 mg/ml) an increased degranulation of EL from PMN of both neonates and adults (317 % and 170 %) could be observed while LF release was found to be increased from neonatal cells only (267 % and 113 % respectively). PTX inhibited meconium-induced EL release in blood of bath neonates and adults by 63 % and 66 %, while LF release was inhibited by 72 % and 57 % respectively. Neonatal PMN exhibit an increased degranulation from azurophilic and specific granules compared with cells from adults. PTX was found to be an effective inhibitor of spontaneous and meconium induced PMN degranulation and may offer new therapeutic options.