formyl-methionyl-delta(z)-dehydroleucyl-phenylalanine-methyl-ester and formylmethionyl-leucyl-phenylalanine-methyl-ester

For-Met-Delta(z)Leu-Phe-OMe ([Delta(z)Leu(2)]) is a conformationally restricted for-Met-Leu-Phe-OMe (fMLP-OMe) analogue able to discriminate between different responses of human neutrophils. In contrast, [Delta(z)Leu(2)] significantly activates the transduction pathways-involving Ca(2+), inositol phosphate, and cyclic AMP (cAMP) enhancement, as is the case with the full agonist fMLP-OMe. Here, we have studied the specific involvement of protein kinase C (PKC) isoforms and mitogen activated protein kinases (MAPKs) in the presence or absence of extracellular Ca(2+), being the cation clearly involved in the activation of neutrophils by fMLP. A strong correlation has been found between PKC isoforms, MAPKs and the selective physiological functions by [Delta(z)Leu(2)]-activated neutrophils. In a calcium-free condition, our data suggest that the failure of PKC beta1 translocation and of p38 MAPK phosphorylation by the analogue refers to its inability to induce chemotaxis, and that the failure by both fMLP-OMe and [Delta(z)Leu(2)] to evoke extracellular response kinase 1 and 2 (ERK1/2) phosphorylation would suggest a reduction in superoxide anion production.

Topics: Calcium; Calcium Signaling; Cells, Cultured; Chemotaxis, Leukocyte; Enzyme Activation; Humans; In Vitro Techniques; Mitogen-Activated Protein Kinase Kinases; N-Formylmethionine Leucyl-Phenylalanine; Neutrophils; Phosphorylation; Protein Kinase C; Superoxides

The increase in human neutrophil cyclic adenosine monophosphate (cAMP) levels evoked by formylated peptides is significantly reduced in the presence of MDL 12330A, SQ 22536, GDPssS and clonidine, which inhibit the adenylyl cyclase system by acting at different sites in this enzyme complex. A similar effect is exerted by adenosine deaminase and dipyridamole, which alter the extracellular adenosine concentration. Neutrophil preincubation with adenylyl cyclase inhibitors or dipyridamole reduces chemotaxis and superoxide anion production triggered by peptides; adenosine deaminase, on the contrary, has no effect on neutrophil responses. Our results seem to indicate that: (1) the peptide-induced increase in neutrophil cAMP is due mainly to an action on the adenylyl cyclase system; (2) an enhancement of this cyclic nucleotide, even slight and necessarily transient, is required for chemotaxis and O2 production induced in neutrophils by formylated peptides; and (3) cAMP does not represent the crucial second messenger for adenosine in the modulation of neutrophil responses.

Topics: Adenosine; Adenosine Deaminase; Adenylyl Cyclase Inhibitors; Chemotaxis, Leukocyte; Cyclic AMP; Dipyridamole; Enzyme Inhibitors; Humans; N-Formylmethionine Leucyl-Phenylalanine; Neutrophils; Superoxides

For-Met-delta ZLeu-delta ZPhe-OMe (3) has been synthesized as a new analogue of the prototypical chemotactic agent For-Met-Leu-Phe-OMe (fMLP-OMe). Compound 3 is characterized by presence of two consecutive alpha,beta-didehydro amino acid residues [delta ZLeu = (Z)-alpha,beta-didehydroleucine; delta ZPhe = (Z)-alpha,beta- didehydrophenylalanine] located at the central and C-terminal position, respectively. When tested on human neutrophils the N-formyltripeptide 3, although less active than the parent, is able to induce chemotaxis, superoxide anion production and lysozyme release. The activity of 3 has been compared to that of related fMLP-OMe analogues containing a single delta ZPhe residue located at the C-terminal position.

Topics: Amino Acid Sequence; Chemotactic Factors; Humans; Molecular Sequence Data; N-Formylmethionine Leucyl-Phenylalanine; Structure-Activity Relationship