Cytochalasin B triggers a novel pertussis toxin sensitive pathway in TNF-alpha primed neutrophils

• BACKGROUND: Cytochalasin B does not directly activate the oxygen-radical-producing NADPH oxidase activity of neutrophils but transfers desensitized G-protein coupled receptors (GPCR) into an active signaling state by uncoupling GCPR from the cytoskeleton. The receptor uncoupling results in respiratory burst activity when signals generated by reactivated formyl peptide receptors trigger the NADPH-oxidase to produce superoxide anions. RESULTS: Tumor necrosis factor alpha (TNF-alpha) primes neutrophils for subsequent activation by cytochalasin B. Pretreatment with TNF-alpha induced mobilization of receptor-storing neutrophil organelles, suggesting that receptor up-regulation significantly contributes to the response, but the receptor mobilization was not sufficient for induction of the cytochalasin B sensitive state. The TNF-alpha primed state resembled that of the desensitized non-signaling state of agonist-occupied neutrophil formyl peptide receptors. The fact that the TNF-alpha primed, cytochalasin B-triggered activation process was pertussis toxin sensitive suggests that the activation process involves a GPCR. Based on desensitization experiments the unidentified receptor was found to be distinct from the C5a receptor as well as the formyl peptide receptor family members FPR and FPRL1. Based on the fact the occupied and desensitized receptors for interleukin-8 and platelet activating factor could not be reactivated by cytochalasin B, also these could be excluded as receptor candidates involved in the TNF-alpha primed state. CONCLUSIONS: The TNF-alpha-induced priming signals could possibly trigger a release of an endogenous GPCR-agonist, amplifying the response to the receptor-uncoupling effect of cytochalasin B. However, no such substance could be found, suggesting that TNF-alpha can transfer G-protein coupled receptors to a signaling state independently of agonist binding.

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Medicinska och farmaceutiska grundvetenskaper -- Immunologi inom det medicinska området (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Basic Medicine -- Immunology in the medical area (hsv//eng)

Nyckelord

Cyclosporine/pharmacology

Cytochalasin B/*pharmacology

Humans

Imidazoles/pharmacology

NADPH Oxidase/metabolism

Neutrophil Activation/physiology

Neutrophils/*drug effects/enzymology/*physiology

Peptide Fragments/immunology

Pertussis Toxin/*immunology

Protein-Serine-Threonine Kinases/antagonists & inhibitors

Pyridines/pharmacology

Receptors

Formyl Peptide/antagonists & inhibitors/physiology

Receptors

G-Protein-Coupled/physiology

Respiratory Burst/drug effects

Secretory Vesicles/metabolism

Signal Transduction/*physiology

Tumor Necrosis Factor-alpha/*pharmacology/physiology

Publikations- och innehållstyp

ref (ämneskategori)

art (ämneskategori)