Modulation of neutrophil phospholipase C activity and cyclic AMP levels by fMLP-OMe analogues.
The N-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP)-OMe (1) analogues for-Thp-Leu-Ain-OMe (2), for-Thp-Leu-Phe-OMe (3), for-Met-Leu-Ain-OMe (4), for-Met-Delta(z)Leu-Phe-OMe (5), for-Met-Lys-Phe-For-Met-Lys-Phe (6), for-Met-Leu-Pheol-COMe (7), and for-Nle-Leu-Phe-OMe (8) have been studied. Some of these have been found selective towards the activation of different biological responses of human neutrophils. In particular, peptides 2 and 3, which evoke only chemotaxis, are ineffective in enhancing inositol phosphate, as well as cyclic AMP (cAMP) levels. On the contrary, analogues 5 and 7, which induce superoxide anion production and degranulation, but not chemotaxis, significantly increase the levels of the two intracellular messengers, as is the case of the full agonists 1 and 6. The Ca(2+) ionophore A23187 also activates phospholipase C (PLC) and increases the nucleotide levels; when tested in combination with peptide 1 or 5, a supra-additive enhancement of cAMP concentration is obtained. The PLC blocker, U-73122, inhibits the formylpeptide-induced inositol phosphate formation, as well as cAMP increase. Moreover, this drug drastically reduces superoxide anion release triggered by 1 or 5, whereas it inhibits to a much lesser extent neutrophil chemotaxis induced by 1 or 2. Our results suggest that: (i) PLC stimulation is involved in cAMP enhancement by formylpeptides; (ii) the activation of PLC by formylpeptides, in conditions of increased Ca(2+) influx, induces a supra-additive enhancement of the nucleotide; (iii) the inability of pure chemoattractants to significantly alter the PLC activity or cAMP level, differently from full agonists or peptides specific in inducing superoxide anion release, appears as a general property. Thus, the activation of neutrophil PLC seems essential for superoxide anion release, but less involved in the chemotactic response.
Ferretti
M E
ME
Dipartimento di Biologia, Sezione di Fisiologia Generale, via L. Borsari 46, Università di Ferrara, 44100, Ferrara, Italy.
Nalli
M
M
Biondi
C
C
Colamussi
M L
ML
Pavan
B
B
Traniello
S
S
Spisani
S
S
D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D002634:Chemotaxis, Leukocyte; D000242:Cyclic AMP / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004963:Estrenes / Q000494:pharmacology; D006801:Humans; D007476:Ionophores / Q000494:pharmacology; D008024:Ligands; D008956:Models, Chemical; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000031:analogs & derivatives / Q000494:pharmacology*; D009504:Neutrophils / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D011760:Pyrrolidinones / Q000494:pharmacology; D013481:Superoxides / Q000378:metabolism; D013997:Time Factors; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism*
D004791:Enzyme Inhibitors; D004963:Estrenes; D007476:Ionophores; D008024:Ligands; D011760:Pyrrolidinones; D013481:Superoxides; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D000001:Calcimycin; D009240:N-Formylmethionine Leucyl-Phenylalanine; C042932:formylmethionyl-leucyl-phenylalanine methyl ester; D000242:Cyclic AMP; D010738:Type C Phospholipases; D002118:Calcium