Neutrophil beta-adrenergic receptor responses are potentiated by acute exposure to phorbol ester without changes in receptor distribution or coupling.
Exposure to the phorbol ester, phorbol 12-myristate, 13-acetate (PMA, 100nM) for 10 minutes enhanced cyclic AMP accumulation in human neutrophils under basal conditions and in response to the beta-adrenergic receptor agonist isoproterenol (ISO), 1 microM) and the adenylate cyclase activator forskolin (FSK, 10mM). Potentiation of responses to ISO by PMA was dose-dependent between 0.1 and 100nM PMA. The diacylglycerol analogue, 1-oleoyl-2-acetylglycerol (OAG) (50 microM) also elevated beta-receptor responses, but 4 beta-phorbol (100nM), lacking the capacity to activate PMA, was ineffective. Short-term exposure (12 seconds) to the peptide n-formylmethionine leucyl-phenylalanine (FMLP, 1 microM) also elevated neutrophil cyclic AMP accumulation. All potentiating effects of PMA on cyclic AMP production were inhibited by the protein kinase inhibitor 1-(5-isoquinolinylsulphonyl)-2-methylpiperazine (H7). Elevation of cyclic AMP by FMLP was insensitive to H7. PMA had no apparent effect on beta-receptor agonist-affinity, distribution between cell-surface and internalised compartments, or the capacity of ISO to induce beta-receptor internalisation. Responses to FSK or ISO in terms of fold-stimulation of basal cyclic AMP accumulation in the presence of PMA were not elevated by PMA. These findings indicate that PMA exerts a potentiating effect on neutrophil adenylate cyclase responses through protein kinase C activation. FMLP elevation of neutrophil cyclic AMP in the absence of other stimuli, appears however, to be insensitive to protein kinase inhibition.
Kilfeather
S A
SA
Department of Clinical Pharmacology, Royal College of Surgeons in Ireland, Dublin.
Stein
M
M
O'Malley
K
K
D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D004075:Diglycerides / Q000494:pharmacology; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000378:metabolism; D009504:Neutrophils / Q000378:metabolism*; D047428:Protein Kinase Inhibitors; D011943:Receptors, Adrenergic, beta / Q000187:drug effects* / Q000502:physiology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
D004075:Diglycerides; D047428:Protein Kinase Inhibitors; D011943:Receptors, Adrenergic, beta; D005576:Colforsin; D009240:N-Formylmethionine Leucyl-Phenylalanine; C038237:1-oleoyl-2-acetylglycerol; D000242:Cyclic AMP; D007545:Isoproterenol; D013755:Tetradecanoylphorbol Acetate