phosphatidylethanol and 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.

Topics: Adult; Age Factors; Aged; Calcium; Diglycerides; Glycerophospholipids; Humans; In Vitro Techniques; Inositol 1,4,5-Trisphosphate; Luminescent Measurements; Membrane Potentials; Middle Aged; N-Formylmethionine Leucyl-Phenylalanine; Neutrophils; Phosphatidic Acids; Phospholipase D; Polycythemia Vera; Receptors, Formyl Peptide; Receptors, Immunologic; Respiratory Burst; Signal Transduction; Superoxides; Tetradecanoylphorbol Acetate; Type C Phospholipases