Beta-adrenergic stimulation down-regulates neutrophil priming for superoxide generation, but not elastase release.
Platelet-activating factor (PAF) concordantly primes neutrophils (PMNs) for superoxide generation and elastase release. beta-Adrenergic stimulation of PMNs enhances cAMP-dependent protein kinase A (PKA) activity and has been shown to inhibit PAF-mediated NADPH-oxidase activity. PMN superoxide generation is thought to play a predominate microbicidal role, whereas elastase is known to mediate untoward PMN-endothelial interactions. We hypothesized that beta-adrenergic neutrophil stimulation has disparate effects on PAF-mediated PMN superoxide generation versus elastase release. Human PMNs were isolated using a standard Ficoll/Hypaque gradient. PMNs were then primed with PAF (200 nM) and activated with fMLP (1 microM). Subsets of PMNs were pretreated for 5 min with a beta agonist (10(-4) M isoprotereno) or an adenylate cyclase agonist (10(-5) M forskolin). Superoxide generation was determined by superoxide dismutase inhibitive cytochrome c reduction. Elastase activity was measured by the cleavage of n-methoxylsuccinyl-A-A-P-V-p-nitroanilide. Pretreatment with isoproterenol and forskolin yielded superoxide generation of 3.2 +/- 0.6 and 3.1 +/- 1.2 nmole/2.5 x 10(5) PMN/min compared to 9.0 +/- 0.6 nmole/2.5 x 10(5) PMN/min for PAF/fMLP alone, whereas isoproterenol and forskolin did not significantly affect PAF-mediated neutrophil elastase release, 22.4 +/- 5.3 and 24.0 +/- 3.6%, respectively, compared to 39.4 +/- 9.1% for PAF/fMLP alone. Disparate PMN signal transduction for superoxide generation versus elastase release may explain the SICU clinical paradox, in which patients are both susceptible to infection and vulnerable to PMN-mediated multiple organ failure.
Barnett
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CC
Department of Surgery, Denver General Hospital, Colorado, USA.
Moore
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EE
Partrick
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DA
Silliman
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CC
D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D015536:Down-Regulation; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology*; D019272:Leukocyte Elastase / Q000378:metabolism*; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D009504:Neutrophils / Q000378:metabolism*; D010972:Platelet Activating Factor / Q000494:pharmacology; D011943:Receptors, Adrenergic, beta / Q000502:physiology*; D013481:Superoxides / Q000378:metabolism*
D000318:Adrenergic beta-Agonists; D010972:Platelet Activating Factor; D011943:Receptors, Adrenergic, beta; D013481:Superoxides; D005576:Colforsin; D009240:N-Formylmethionine Leucyl-Phenylalanine; D019272:Leukocyte Elastase; D007545:Isoproterenol