Proinflammatory interactions of pneumolysin with human neutrophils

The effects of pneumolysin on the proinflammatory activity of human neutrophils, as well as on cation fluxes in these cells, have been investigated. Superoxide production, release of elastase, CR3 expression, phospholipase A(2) activity, and alterations in membrane potential were measured by use of lucigenin-enhanced chemiluminescence and colorimetric, flow cytometric, radiometric, and spectrofluorimetric procedures, respectively; and cation fluxes were measured by use of Ca-45(2+) and Rb-86(+) and by fura-2 spectrofluorometry. Pneumolysin at concentrations >1.67 ng/mL caused influx of Ca2+ and increased phospholipase A(2) activity and CR3 expression, which were associated with enhanced superoxide production and release of elastase after activation of the cells with the chemotactic tripeptide FMLP. At the same concentrations, pneumolysin caused efflux of K+ and membrane depolarization. The effects of pneumolysin on cation fluxes were not attributable to inhibition of Ca2+-adenosine triphosphatase (ATPase) or Na+,K+-ATPase. Pneumolysin potentiates the proinflammatory activities of neutrophils by a pore-forming mechanism resulting in Ca2+ influx.