THERMAL INJURY-INDUCED PRIMING EFFECT OF NEUTROPHIL IS TNF-α AND P38 DEPENDENT

Abstract

Priming response of neutrophil in clinical-related conditions and its mechanism has not been clarified. This study is to determine if thermal injury-induced priming effect of neutrophil is TNF-alpha and p38 dependent. In Experiment 1, bone marrow neutrophil of wild-type (WT) mice and TNF receptor superfamily, member 1A (Tnfrsf1a-/-) mice were harvested and treated with TNF-alpha, platelet activating factor (PAF) first, then with or without N-formyl-Met-Leu-Phe (fMLP). Reactive oxygen species (ROS) production and p38 phosphorylation were evaluated. In Experiment 2, ROS of neutrophil from WT and Tnfrsf1a-/- mice at 3 or 15 h after thermal injury with or without fMLP treatment were assayed. In Experiment 3, p38 and p44/42 phosphorylation, CXCR2 and macrophage inflammatory protein-2 expression, apoptotic ratio, and activating protein-1 (AP-1) and nuclear factor-kappa B (NF-kappaB) activation of neutrophil from WT and Tnfrsf1a-/- mice at 3 h after thermal injury were tested. FMLP treatment after TNF-alpha or PAF incubation of neutrophil increased ROS of PAF-treated but not TNF-alpha-treated neutrophil. PAF treatment increased ROS of neutrophil in WT and Tnfrsf1a-/- mice. FMLP increased ROS of neutrophil of WT mice at 3 h after thermal but not that of Tnfrsf1a-/- mice. TNF-alpha and PAF increased p38 phosphorylation of neutrophil in WT but not that in Tnfrsf1a-/- mice. Thermal injury increased p38 phosphorylation, NF-kappaB activation, and decreased apoptosis of neutrophil at 3 h after thermal injury in WT but not in Tnfrsf1a-/- mice. Thermal injury also induced AP-1 activation and ROS production on neutrophil at 3 and 15 h after thermal injury, respectively, in WT and Tnfrsf1a-/- mice. Collectively, fMLP stimulates ROS of neutrophil through TNF-alpha signaling; PAF stimulates that of neutrophil through both TNF-alpha-dependent and TNF-alpha-independent pathway. Thermal injury induces a TNF-alpha-dependent priming effect and a TNF-alpha-independent activation effect on neutrophil at 3 and 15 h after thermal injury, respectively. NF-kappaB signaling pathway plays an important role in neutrophil activation. Thermal injury also induces TNF-alpha-dependent delay apoptosis and TNF-alpha-independent AP-1 activation of neutrophil at 3 h after thermal injury. Taken together with the TNF-alpha-dependent p38 and NF-kappaB activation in primed neutrophil, we conclude that thermal injury-induced priming effect of polymorphonuclear neutrophil is TNF-alpha and p38 dependent.