Sphingosine 1-phosphate antagonizes human neutrophil apoptosis via p38 mitogen-activated protein kinase

Sphingosine 1-phosphate (SPP) is associated with the regulation of apoptosis, although its role in neutrophil apoptosis remains poorly investigated. Here, we show that exogenous SPP antagonizes spontaneous and anti-Fas-induced apoptosis in neutrophils. Pre-treatment with pertussis toxin clearly reduced the apoptosis-inhibiting capacity of SPP. Consequently, we investigated the involvement of potential modulators of apoptosis that are activated downstream of Gi/G0-coupled receptors. Neither Akt activity nor change in basal activity of c-Jun N-terminal kinases was detected during apoptosis or after adding SPP. In contrast, there was a transient decrease in phosphorylation of both extracellular-regulated kinase (ERK) and p38 mitogen-activated protein kinase (MAPK) during both spontaneous and anti-Fas-induced apoptosis. Although exogenous SPP reversed these reductions in kinase activity, experiments with inhibitors of ERK (PD98059) and p38 MAPK (SB203580) revealed that only SB203580 counteracted the effect of SPP. Thus, SPP counteracts neutrophil apoptosis via a Gi/G0 protein survival-signalling pathway that includes modulation of p38 MAPK activity.