Inhibition of phorbol ester stimulated superoxide production by 1‐oleoyl‐2‐acetyl‐sn‐glycerol (OAG); fact or artefact?

Abstract

OAG-stimulated superoxide (O⁻ ₂) production by HL-60 granulocytes showed enantiomeric specificity but reached a maximum of only 5% of that produced by either phorbol myristate acetate (PMA) or phorbol dibutyrate (PDBu). At 10–100 μM, OAG displaced specifically-bound [³H]PDBu from intact HL-60 cells by only 25%, suggesting limited cell penetration. OAG (10–100 μM) also inhibited PDBu-stimulated O₂ production by 25%; this inhibition was enantiomerically specific. However, at a lower concentration (3 μM), both enantiomers of OAG fully blocked O⁻ ₂ production stimulated by PMA (0.5 μM). This inhibition is probably artefactual, due to the hydrophobic PMA physically associating with OAG in the extracellular fluid.