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Staphylococcal serine proteinase (SSP) can influence various functions of human polymorphonuclear leukocytes (PMNL) including chemotaxis and phagocytosis. Since the rise in intracellular free calcium concentration is an important step in signal transduction leading to phagocyte activation, we tested the ability of SSP to increase the intracellular free calcium concentration in human PMNL using the fluorescent calcium indicator Fura-2AM. PMNL isolated from healthy donors responded to SSP in the concentration range of 10 to 100 micrograms/ml. The highest Ca2+ rise (104 +/- 47 nM) was observed for 10 micrograms/ml SSP. It was mainly dependent (81 +/- 11%) on extracellular calcium influx, however, SSP mobilized 68 +/- 7% of Ca2+ from intracellular calcium stores. Boiling of SSP or preincubation with phenylmethylsulphonylfluoride (an serine proteinase inhibitor) did not change its ability to increase intracellular free calcium concentration in PMNL. It suggests that active center of SSP is not responsible for Ca2+ mobilization. Finally, PMNL responded to each of three consecutive stimulations with SSP independently of the presence of high or low extracellular Ca2+ concentration. This may be an additional mechanism responsible for activation of human PMNL and degradation of alveolar walls during the staphylococcal infection in the lower airways.

During staphylococcal pneumonia massive destruction of lung tissue is often observed. Staphylococcal serine proteinase (SSP) inactivates alpha-1-proteinase inhibitor (alpha 1PI) a major factor which protects lungs from phagocyte proteases. We investigated the effect of SSP on elastin degradation by porcine pancreatic elastase (PE) and crude extract of human neutrophil elastase (NE) in solution and gel containing alpha 1PI. SSP having no elastase activity enhanced PE and NE-induced elastinolysis in solution when added to alpha 1PI before mixing with elastase and then with elastin. SSP added simultaneously with alpha 1PI to PE had no influence on elastin degradation. However, SSP added simultaneously, 30 min before or 30 min after PE significantly increased elastin digestion in elastin-agarose plate with alpha 1PI. Maximal increase in elastinolysis about 3-fold was for SSP added 30 min prior to PE. Since elastin is the major component of the alveolar walls it is possible that lung damage in the course of staphylococcal infection may partly depend on action of SSP.