Superoxide anion production and phospholipase D-mediated generation of diacylglycerol are subnormal after N-formyl-methionyl-leucyl-phenylalanine stimulation of polymorphonuclear granulocytes in polycythemia vera.
We have assessed aspects of the stimulus response coupling for generation of superoxide anions (O2-) in polymorphonuclear granulocytes (PMNs) from patients with polycythemia vera (PV). Those cells exhibited less than half of the O2- secretion that PMNs from healthy controls did, when that response was initiated by N-formyl-methionyl-leucyl-phenylalanine (fMLP), 0.35 +/- 0.38 nmol O2-/10(6) PMNs/min and 0.83 +/- 0.45 nmol O2-/10(6) PMNs/min, respectively (p < 0.02). In contrast, when induced by phorbol myristate acetate (PMA), O2- production in PV PMNs was normal (6.9 +/- 1.1 nmol O2-/10(6) PMNs/min vs 6.9 +/- 0.6 nmol O2-/10(6) PMNs/min for control cells). In an attempt to dissect this stimulus-specific dichotomy of the oxidative responsiveness of PV PMNs, we analyzed the number of and ligand affinity for fMLP surface receptors, fMLP-induced membrane potential changes, phospholipase C-dependent production of inositol-1,4,5-trisphosphate, and the subsequent rise of cytosolic calcium concentrations. All these variables and responses were normal in PV PMNs. However, on fMLP stimulation of PV PMNs, we observed a significantly lower diacylglycerol (DAG) generation than in control cells (1.4% +/- 0.9% and 2.2% +/- 1.2% DAG of total phospholipid, respectively; p < 0.05). Furthermore, the activation of phospholipase D, measured as the formation of phosphatidylethanol (PET) in the presence of 0.5% ethanol, was impaired in PV PMNs with a similar stimulus-specific dichotomy as observed for O2- generation. Thus PET generation was significantly lower in PV cells after fMLP stimulation in relation to control cells (1.7% +/- 0.8% and 2.7% +/- 0.8% PET of total phospholipid, respectively; p < 0.01), whereas PET formation after PMA stimulation did not differ. We suggest that the impairment of phospholipase D-mediated metabolism of phosphatidylcholine in response to fMLP stimulation of polycythemia vera granulocytes may be of significance for the reduced superoxide anion formation induced by fMLP in those cells.
Department of Medicine, Stockholm Söder Hospital, Sweden.
J
J
Samuelsson
A
A
Hansson
K
K
Rosendahl
J
J
Palmblad
D000328:Adult; D000367:Age Factors; D000368:Aged; D002118:Calcium / Q000378:metabolism; D004075:Diglycerides / Q000378:metabolism*; D020404:Glycerophospholipids; D006801:Humans; D066298:In Vitro Techniques; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D008163:Luminescent Measurements; D008564:Membrane Potentials; D008875:Middle Aged; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology*; D009504:Neutrophils / Q000502:physiology*; D010712:Phosphatidic Acids / Q000378:metabolism; D010739:Phospholipase D / Q000378:metabolism*; D011087:Polycythemia Vera / Q000378:metabolism*; D044042:Receptors, Formyl Peptide; D011971:Receptors, Immunologic / Q000502:physiology; D016897:Respiratory Burst; D015398:Signal Transduction; D013481:Superoxides / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D010738:Type C Phospholipases / Q000378:metabolism
D004075:Diglycerides; D020404:Glycerophospholipids; D010712:Phosphatidic Acids; D044042:Receptors, Formyl Peptide; D011971:Receptors, Immunologic; C051521:phosphatidylethanol; D013481:Superoxides; D009240:N-Formylmethionine Leucyl-Phenylalanine; D015544:Inositol 1,4,5-Trisphosphate; D010738:Type C Phospholipases; D010739:Phospholipase D; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium