Proinflammatory interactions of pneumolysin with human neutrophils

The effects of pneumolysin on the proinflammatory activity of human neutrop hils, as well as on cation fluxes in these cells, have been investigated. S uperoxide 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, rad iometric, and spectrofluorimetric procedures, respectively; and cation flux es were measured by use of Ca-45(2+) and Rb-86(+) and by fura-2 spectrofluo rometry. Pneumolysin at concentrations >1.67 ng/mL caused influx of Ca2+ an d increased phospholipase A(2) activity and CR3 expression, which were asso ciated with enhanced superoxide production and release of elastase after ac tivation of the cells with the chemotactic tripeptide FMLP. At the same con centrations, pneumolysin caused efflux of K+ and membrane depolarization. T he effects of pneumolysin on cation fluxes were not attributable to inhibit ion of Ca2+-adenosine triphosphatase (ATPase) or Na+,K+-ATPase. Pneumolysin potentiates the proinflammatory activities of neutrophils by a pore-formin g mechanism resulting in Ca2+ influx.