Involvement of bivalent cations and arachidonic acid in neutrophil aggregation

Abstract

Chemotactic factors and arachidonic acid aggregate neutrophils; indomethacin and 5,8,11,14-eicosatetraynoic acid, two blockers of cellular arachidonate metabolism, inhibit these responses. Additionally, A23187, an ionophore which specifically transports bivalent cations into cells, also aggregates the neutrophils, and this response, as well as the response to chemotactic factors, requires the presence of extracellular calcium and magnesium. In this report these relationships were further studied. It was found that human neutrophil aggregation stimulated by arachidonic acid required calcium and magnesium. Furthermore, cells preincubated with arachidonate for 4 min before exposure to the bivalent cations did not aggregate before or after this exposure and, following this exposure, were refractory to subsequent stimulation by more arachidonate, a chemotactic tripeptide (formylmethionylleucylphenylalanine), or A23187, i.e., these cells had become nonselectively desensitized to the aggregating agents. Finally, indomethacin and 5,8,11,14-eicoasatetraynoic acid inhibited the aggregation response stimulated by A23187 and their potency in doing so paralleled their potency in inhibiting the responses induced by arachidonate or the chemotactic tripeptide. Thus, the neutrophil aggregation responses induced by arachidonate, chemotactic factor, and A23187 were similarly influenced by preincubating the cells with arachidonate, had similar requirements for calcium and magnesium, and were similarly inhibited by blockers of arachidonate metabolism. It appears that bivalent cations and arachidonic acid play essential and, perhaps, interacting roles in the aggregation response to diverse stimuli.

Neutrophils in innate host defense against Staphylococcus aureus infections

“…Biochemical studies that continued through the late 1980s and early 1990s characterized in detail, additional, important capabilities of neutrophils including the assembly and activation of the phagocyte NADPH oxidase, mechanistic functions of granule proteins, the role of actin in the mobilization of phagocytic cells, and the discovery that bacterial-derived N-formyl peptides induce chemotaxis and enhance microbicidal functions of neutrophils [81–90]. These studies quickly drew additional interest, sparking the use of neutrophils as model host cells for the study of new signal transduction pathways that included calcium transients, phosphorylation events, G protein-coupled receptors, and phospholipid signaling and metabolism [91–100]. Further validation of the diversity and importance of neutrophil function came with the more recent description of mechanisms underlying normal neutrophil turnover, which we now know occurs by spontaneous or constitutive apoptosis.…”