cytochalasin-b and Hypereosinophilic-Syndrome

This study was undertaken to identify the signaling events involved in activation of neutrophil superoxide anion (O2-) production by eosinophil granule major basic protein (MBP). MBP did not produce an immediate increase in the cytosolic free calcium concentration ([Ca2+]i), characteristic of phospholipase C activation, but did cause a gradual increase in [Ca2+]i in cytochalasin B-treated cells. Preincubation with 0.01 to 3 micrograms/mL pertussis toxin did not inhibit MBP-stimulated O2- production, and MBP did not stimulate an increase in diradylglycerol levels. MBP did stimulate a low level of phospholipase D activity, as measured by a time-dependent increase in phosphatidic acid and, in the presence of 0.5% ethanol, phosphatidylethanol. Inhibition of MBP-stimulated O2- production by genistein and Western blot analysis using an antiphosphotyrosine antibody showed tyrosine kinase activation by MBP. Calmodulin antagonists (calmidazolium and W-7) caused up to 80% inhibition of MBP-stimulated O2- production. In agreement with the pharmacologic sensitivity, MBP did not stimulate any 51Cr release. These data indicate that tyrosine kinase and calmodulin-dependent steps are involved in the noncytotoxic stimulation of neutrophil O2- production by MBP.

Topics: Blood Proteins; Calcium; Calmodulin; Cytochalasin B; Diglycerides; Eosinophil Granule Proteins; Genistein; Humans; Hypereosinophilic Syndrome; Isoflavones; N-Formylmethionine Leucyl-Phenylalanine; Neutrophils; Pertussis Toxin; Phospholipase D; Phospholipids; Protein-Tyrosine Kinases; Respiratory Burst; Ribonucleases; Signal Transduction; Superoxides; Virulence Factors, Bordetella