Intracellular signaling events in superoxide generation and adhesion of channel catfish, Ictalurus punctatus rafinesque, neutrophils to the extracellular matrix protein fibrinogen.

Activation of channel catfish neutrophils is essential if these cells are to participate in adhesion to extracellular matrix proteins or generate intracellular superoxide for killing of microbes. Various signaling pathways are required for these activities to occur. The objective of this study was to identify components of the signal transduction pathways in channel catfish neutrophils. A23187, bryostatin, and phorbol dibutyrate (PDBU) all induced catfish neutrophil adhesion to fibrinogen coated plates and the adhesion could be significantly reduced when neutrophils were pretreated with staurosporine (1 x 10(-7) M). Staurosporine was the only inhibitor used in the study that inhibited or reduced PDBU-induced adhesion of catfish neutrophils to fibrinogen. Phorbol dibutyrate at the concentrations used in the adhesion assay was the only stimulant that caused generation of intracellular superoxide and therefore was the only stimulant used in the remainder of the study. Aristolochic acid (1 x 10(-4) and 3 x 10(-5) M) + PDBU and staurosporine (1 x 10(-7) and 1 x 10(-8) M) + PDBU caused a significant decrease (p < or = 0.05) in PDBU-induced intracellular oxygen generation. The role of protein kinase C and phospholipases in channel catfish neutrophil adhesion and superoxide generation are discussed.