Neutrophil priming has been implicated in the development of multiple organ failure, although the precise intracellular mechanisms that regulate neutrophil priming remain unclear. Our previous work characterized platelet-activating factor (PAF) priming of human neutrophils for concordant superoxide anion (O2−) generation and elastase degranulation. The p38 mitogen-activated protein kinase (MAPK) is activated by PAF stimulation. We hypothesized that PAF-induced human neutrophil priming for O2− and elastase release is mediated via the p38 MAPK pathway.
Isolated neutrophils from 6 human donors were preincubated with the specific p38 MAPK inhibitor SB 203580 (1 µmol/L) or buffer (control) for 30 minutes. Cells were then primed with PAF (200 nmol/L), followed by receptor-dependent (N-formyl-methionyl-leucyl-phenylalanine, 1 µmol/L) or receptor-independent phorbol myristate acetate (PMA, 100 ng/mL) activation.
Urban trauma research laboratory.
Healthy volunteer donors of neutrophils.
Main Outcome Measures
Maximal rate of O2− generation was measured by superoxide dismutase-inhibitable reduction of cytochrome c and elastase release by the cleavage of N-methoxysuccinyl-Ala-Ala-Pro-Val-p-nitroanilide.
SB 203580 significantly attenuated the generation of O2− and release of elastase from neutrophils activated with N-formyl-methionyl-leucyl-phenylalanine but not with PMA. Independent of the activator receptor status, SB 203580 almost completely blocked the exaggerated neutrophil cytotoxic response due to PAF priming.
The p38 MAPK pathway is required for maximal PAF-induced neutrophil priming for O2− production and elastase degranulation. Therefore, the MAPK signaling cascade may offer a potential therapeutic strategy to preempt global neutrophil hyperactivity rather than attempt to nullify the end products independently.