Neutrophil NADPH-oxidase activation by an annexin AI peptide is transduced by the formyl peptide receptor (FPR), whereas an inhibitory signal is generated independently of the FPR family receptors

Truncation of the N-terminal part of the calcium-regulated and phospholipid-binding protein annexin AI has been shown to change the functional properties of the protein and to generate immunoregulatory Peptides. Proinflammatory as well as anti-inflammatory signals are triggered by these Peptides, and the two formyl peptide receptor (FPR) family members expressed in neutrophils, FPR and FPR-like 1 (FPRL1), have been suggested to transduce these signals. We now report that an annexin AI peptide (Ac9-25) activates, as well as inhibits, the neutrophil release of superoxide anions. Results obtained from experiments with receptor antagonists/inhibitors, desensitized cells, and transfected cells reveal that the Ac9-25 peptide activates the neutrophil reduced nicotinamide adenine dinucleotide phosphate oxidase through FPR but not through FPRL1. The Ac9-25 peptide also inhibits the oxidase activity in neutrophils triggered, not only by the FPR-specific agonist N-formyl-Met-Leu-Phe but also by several Other agonists operating through different G protein-coupled receptors. Our data show that the two signals generated by the Ac9-25 peptide are transmitted through different receptors, the inhibitory signal being transduced by a not-yet identified receptor distinct from FPR and FPRL1.