Effects of phosphodiesterase (III/IV)-inhibitors and cytokines on mechanical properties of neutrophilic granulocytes in neonates and adults

Abstract

Sequestration of activated PMN and enrichment in tissues play a key role in tissue damage during septicaemia and after ischemia/reperfusion. Since polymorphonuclear neutrophilic granulocytes (PMN) of term neonates show various functional differences compared to PMN in adults (decreased chemotaxis, decreased intracellular killing, decreased adhesion) we studied the influence of interleukin 8 (IL-8), tumor necrosis factor-α (TNF-α) and N-formyl-methionyl-leucyl-phenylalanine (fMLP) on the reduction of deformability of PMN in neonates and adults. The following phosphodiesterase (PDE)-inhibitors were applied to ameliorate the reduction in deformability when the PMN were stimulated with fMLP or IL-8: Enoximone, Milrinone (PDE-III-inhibitors), Pentoxifylline (PTX) and Piclamilast (PDE-IV-inhibitors). The micropipette technique and the cell transit analyzer (CTA) were used and compared. Aspiration times into micropipettes with an internal diameter of 5 μm, transit times through 8 μm filter pores and neutrophil elastase concentrations were determined. Despite of the functional differences of PMN in neonates compared to adults the significant decrease of deformability of PMN activated with cytokines compared to passive PMN was not different in both groups. The neutrophil elastase concentrations reflect the activation of the PMN: highest concentrations during activation, decreased concentrations due to PDE-inhibitors, and PMN in a passive state. The neutrophil elastase concentrations were not different from PMN of neonates and adults. These PDE-inhibitors significantly increased the deformability of activated PMN but significant differences between the deformability of PMN in neonates and adults were not found. Despite the functional differences of PMN in neonates PDE-III/IV-inhibitors lead to similar improvement of mechanical properties of activated PMN in neonates and adults. These drugs may ameliorate impaired microcirculation also in neonates during inflammation.