Figure 7.

rPLY and rSLO induce platelet aggregation via pore dependent calcium influx. The cytotoxicity of rPLY (A) and rSLO (B) against platelets and the cholesterol inhibiting effect were assessed by an LDH assay (Methods Section). (C) The cholesterol (100 μg/mL) effect on rPLY (0.8 μg/mL)- and rSLO (1.5 μg/mL)-induced platelet aggregation. (D) The EGTA (3 mM) effect on rPLY (0.8 μg/mL)- and rSLO (1.5 μg/mL)-induced PNA formation. PBS acted as the negative control for the recombinant proteins. Cholesterol and EGTA were dissolved in ethanol and H₂O, respectively. Unpaired t-test with Welch's correction was used for (A,B,D) statistical analyses. Unpaired two-tailed Student's t-test was used for (C) statistical analysis. Data in panels (A–D) are given as the mean ± SD of three independent experiments, with each experiment using blood from a different donor. P < 0.05 is considered to be the threshold for statistical significance; ns, not significant; rPLY, recombinant pneumolysin; rSLO, recombinant streptolysin O; Cho, cholesterol; 0.8+Cho, 0.8 μg/mL of rPLY added to cholesterol; 1.5+Cho, 1.5 μg/mL of rSLO added to cholesterol.