The anti-inflammatory interactions of epinephrine with human neutrophils in vitro are achieved by cyclic AMP-mediated accelerated resequestration of cytosolic calcium.
This study was designed to evaluate the effects of epinephrine (0.01-1 microM) on superoxide production by, and release of elastase from human neutrophils activated with the chemotactic tripeptide, N-formyl-L-methionyl-L-leucyl-L-phenylalanine (FMLP) (1 microM) in vitro, and to relate alterations in these responses to changes in adenosine 3,5' cyclic monophosphate (cAMP) and cytosolic free Ca(2+). Cyclic AMP, superoxide production and elastase release were measured by radioimmunoassay, lucigenin-enhanced chemiluminescence, and a colorimetric procedure respectively. Cytosolic Ca(2+) fluxes were measured by fura-2 spectrofluorimetry in combination with radiometric procedures that enable distinction between net efflux and influx of the cation. Epinephrine treatment of neutrophils resulted in increased cAMP and dose-related inhibition of both superoxide production and elastase release, which was potentiated by the type 4 phosphodiesterase inhibitor, rolipram, and attenuated by propranolol, but not by selective beta(1)-, alpha(1)- or alpha(2)-adrenoreceptor antagonists. Although epinephrine did not affect the FMLP-activated abruptly-occurring increase in fura-2 fluorescence intensity, indicating no effects on the release of Ca(2+) from neutrophil intracellular stores, this agent accelerated the rate of decline in fluorescence in the setting of decreased efflux and a reduction in store-operated influx of Ca(2+). These effects of epinephrine on the clearance of Ca(2+) from the cytosol of FMLP-activated neutrophils were attenuated by propranolol, and are compatible with enhancement of the activity of the cAMP-dependent Ca(2+) sequestering/resequestering endo-membrane Ca(2+)-ATPase. We conclude that epinephrine down-regulates the pro-inflammatory activities of neutrophils by cAMP-mediated enhancement of the clearance of cytosolic Ca(2+).
Tintinger
G R
GR
Department of Internal Medicine, University of Pretoria, South Africa
Theron
A J
AJ
Anderson
R
R
Ker
J A
JA
D000328:Adult; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000378:metabolism; D002132:Calcium Radioisotopes; D000242:Cyclic AMP / Q000378:metabolism; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D004837:Epinephrine / Q000494:pharmacology*; D005456:Fluorescent Dyes / Q000378:metabolism; D016257:Fura-2 / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D018375:Neutrophil Activation / Q000187:drug effects; D009504:Neutrophils / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D010196:Pancreatic Elastase / Q000378:metabolism*; D013481:Superoxides / Q000378:metabolism*; D014662:Vasoconstrictor Agents / Q000494:pharmacology
D002132:Calcium Radioisotopes; D005456:Fluorescent Dyes; D014662:Vasoconstrictor Agents; D013481:Superoxides; D009240:N-Formylmethionine Leucyl-Phenylalanine; D000242:Cyclic AMP; D010196:Pancreatic Elastase; D002118:Calcium; D016257:Fura-2; D004837:Epinephrine