Human tumour necrosis factor-alpha (TNF-alpha) directly stimulates arachidonic acid release in human neutrophils

The ability of tumour necrosis factor-alpha (TNF-alpha) to directly stimulate phospholipid turnover from human neutrophils was studied. Stimulation with recombinant human (rH) TNF-alpha induced the release of significant amounts of radioactivity from [3H]arachidonic acid-labelled neutrophils. This stimulation was equipotent to that induced by the bacterial tripeptide formyl-methionyl-leucylphenylalanine (FMLP). The time of maximum stimulated release varied between donors, with the most common maximal stimulation being 45 min. Dose-response experiments indicated that 100-1000 U/ml rH TNF-alpha were required for the maximum stimulatory effect. High-performance liquid chromatography analysis of the supernatants revealed that the radioactivity was associated with arachidonic acid, but not with its metabolites, indicating that TNF-alpha stimulates the release of arachidonic acid from cellular phospholipids but does not stimulate its metabolism. A comparison of TNF-alpha with other cytokines indicated that stimulation of arachidonic acid release paralleled the 'priming' of neutrophils for enhanced superoxide production, raising the possibility that phospholipid turnover and priming of neutrophils are causally related.