Maximal human neutrophil priming for superoxide production and elastase release requires p38 mitogen-activated protein kinase activation

Hypothesis: Neutrophil priming has been implicated in the development of mu ltiple organ failure, although the precise intracellular mechanisms that re gulate neutrophil priming remain unclear. Our previous work characterized p latelet activating factor (PAF) priming of human neutrophils for concordant superoxide anion (O-2(-)) generation and elastase degranulation. The p38 m itogen-activated protein kinase (MAPK) is activated by PAF stimulation. We hypothesized that PAF-induced human neutrophil priming for O-2(-) and elast ase release is mediated via the p38 MAPK pathway. Design: Isolated neutrophils from 6 human donors were preincubated with the specific p38 MAPK inhibitor SE 203580 (1 mu mol/L) or buffer (control) for 30 minutes. Cells were then primed with PAF (200 nmol/L), followed by rece ptor-dependent (N-formyl-methionyl-leucylphenylalanine, 1 mu mol/L) or rece ptor-independent phorbol myristate acetate(PMA, 100 ng/mL) activation. Setting: Urban trauma research laboratory. Patients: Healthy volunteer donors of neutrophils. Main Outcome Measures: Maximal rate of O-2(-) generation was measured by su peroxide dismutase-inhibitable reduction of cytochrome c and elastase relea se by the cleavage of N-methoxysuccinyl-Ala-Ala-Pro-Val-p-nitroanilide. Results: SE 203580 significantly attenuated the generation of O-2(-) and re lease of elastase from neutrophils activated with N-fornlyl-methionyl-leucy l-phenylalanine but not with PMA. Independent of the activator receptor sta tus: SE 203580 almost completely blocked the exaggerated neutrophil cytotox ic response due to PAF priming. Conclusions: The p38 MAPK pathway is required for maximal PAF-induced neutr ophil priming for O-2(-) production and elastase degranulation. Therefore, the MAPK signaling cascade may offer a potential therapeutic strategy to pr eempt global neutrophil hyperactivity rather than attempt to nullify the en d products independently.